usort

(PHP 4, PHP 5, PHP 7)

usort — Sort an array by values using a user-defined comparison function

Description

bool usort ( array &$array , callable $value_compare_func )

This function will sort an array by its values using a user-supplied comparison function. If the array you wish to sort needs to be sorted by some non-trivial criteria, you should use this function.

Note:
If two members compare as equal, their relative order in the sorted array is undefined.

Note: This function assigns new keys to the elements in array. It will remove any existing keys that may have been assigned, rather than just reordering the keys.

Parameters

array: The input array.
value_compare_func: The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second.

int callback ( mixed $a, mixed $b )

Caution
Returning non-integer values from the comparison function, such as float, will result in an internal cast to integer of the callback's return value. So values such as 0.99 and 0.1 will both be cast to an integer value of 0, which will compare such values as equal.

Return Values

Returns TRUE on success or FALSE on failure.

Examples

Example #1 usort() example


<?php
function cmp($a, $b)
{
    if ($a == $b) {
        return 0;
    }
    return ($a < $b) ? -1 : 1;
}

$a = array(3, 2, 5, 6, 1);

usort($a, "cmp");

foreach ($a as $key => $value) {
    echo "$key: $value\n";
}
?>

The above example will output:

0: 1
1: 2
2: 3
3: 5
4: 6

Note:
Obviously in this trivial case the sort() function would be more appropriate.

Example #2 usort() example using multi-dimensional array


<?php
function cmp($a, $b)
{
    return strcmp($a["fruit"], $b["fruit"]);
}

$fruits[0]["fruit"] = "lemons";
$fruits[1]["fruit"] = "apples";
$fruits[2]["fruit"] = "grapes";

usort($fruits, "cmp");

while (list($key, $value) = each($fruits)) {
    echo "\$fruits[$key]: " . $value["fruit"] . "\n";
}
?>

When sorting a multi-dimensional array, $a and $b contain references to the first index of the array.

The above example will output:

$fruits[0]: apples
$fruits[1]: grapes
$fruits[2]: lemons

Example #3 usort() example using a member function of an object


<?php
class TestObj {
    var $name;

    function TestObj($name)
    {
        $this->name = $name;
    }

    /* This is the static comparing function: */
    static function cmp_obj($a, $b)
    {
        $al = strtolower($a->name);
        $bl = strtolower($b->name);
        if ($al == $bl) {
            return 0;
        }
        return ($al > $bl) ? +1 : -1;
    }
}

$a[] = new TestObj("c");
$a[] = new TestObj("b");
$a[] = new TestObj("d");

usort($a, array("TestObj", "cmp_obj"));

foreach ($a as $item) {
    echo $item->name . "\n";
}
?>

The above example will output:

b
c
d

Example #4 usort() example using a closure to sort a multi-dimensional array


<?php
$array[0] = array('key_a' => 'z', 'key_b' => 'c');
$array[1] = array('key_a' => 'x', 'key_b' => 'b');
$array[2] = array('key_a' => 'y', 'key_b' => 'a');

function build_sorter($key) {
    return function ($a, $b) use ($key) {
        return strnatcmp($a[$key], $b[$key]);
    };
}

usort($array, build_sorter('key_b'));

foreach ($array as $item) {
    echo $item['key_a'] . ', ' . $item['key_b'] . "\n";
}
?>

The above example will output:

y, a
x, b
z, c

User Contributed Notes

zuallauz at gmail dot com

4 years ago


When trying to do some custom sorting with objects and an anonymous function it wasn't entirely clear how this usort function works. I think it probably uses a quicksort in the background. Basically it actually moves the $b variable up or down in respect to the $a variable. It does NOT move the $a variable inside the callback function. This is key to getting your logic right in the comparisons.

If you return -1 that moves the $b variable down the array, return 1 moves $b up the array and return 0 keeps $b in the same place. 

To test I cut down my code to sorting a simple array from highest priority to lowest.

<?php
$priorities = array(5, 8, 3, 7, 3);

usort($priorities, function($a, $b)
{
    if ($a == $b)
    {
        echo "a ($a) is same priority as b ($b), keeping the same\n";
        return 0;
    }
    else if ($a > $b)
    {
        echo "a ($a) is higher priority than b ($b), moving b down array\n";
        return -1;
    }
    else {
        echo "b ($b) is higher priority than a ($a), moving b up array\n";                
        return 1;
    }
});

echo "Sorted priorities:\n";
var_dump($priorities);
?>

Output:

b (8) is higher priority than a (3), moving b up array
b (5) is higher priority than a (3), moving b up array
b (7) is higher priority than a (3), moving b up array
a (3) is same priority as b (3), keeping the same
a (8) is higher priority than b (3), moving b down array
b (8) is higher priority than a (7), moving b up array
b (8) is higher priority than a (5), moving b up array
b (8) is higher priority than a (3), moving b up array
a (5) is higher priority than b (3), moving b down array
a (7) is higher priority than b (5), moving b down array

Sorted priorities:
array(5) {
  [0]=> int(8)
  [1]=> int(7)
  [2]=> int(5)
  [3]=> int(3)
  [4]=> int(3)
}

svenxy AT nospam gmx net

9 years ago


This will sort subnets correctly:

<?php

$zones = 
array('192.168.11',
'192.169.12',
'192.168.13',
'192.167.14',
'192.168.15',
'122.168.16',
'192.168.17'
);

function sort_subnets ($a, $b) {
    $a_arr = explode('.', $a);
    $b_arr = explode('.', $b);
    foreach (range(0,3) as $i) {
        if ( $a_arr[$i] < $b_arr[$i] ) {
            return -1;
        }
        elseif ( $a_arr[$i] > $b_arr[$i] ) {
            return 1;
        }
    }
    return -1;
}

usort($zones, 'sort_subnets');
print '<pre>';
print_r($zones);
print '</pre>';

?>

gmail.com - nmcquay

7 years ago


I wrote a wrapper for usort that lets you use something similar to an SQL ORDER BY clause. It can sort arrays of associative arrays and arrays of objects and I think it would work with some hybrid case.



Example of how the function works:



<?php

$testAry = array(

  array('a' => 1, 'b' => 2, 'c' => 3),

  array('a' => 2, 'b' => 1, 'c' => 3),

  array('a' => 3, 'b' => 2, 'c' => 1),

  array('a' => 1, 'b' => 3, 'c' => 2),

  array('a' => 2, 'b' => 3, 'c' => 1),

  array('a' => 3, 'b' => 1, 'c' => 2)

);



Utility::orderBy($testAry, 'a ASC, b DESC');



//Result:

$testAry = array(

  array('a' => 1, 'b' => 3, 'c' => 2),

  array('a' => 1, 'b' => 2, 'c' => 3),

  array('a' => 2, 'b' => 3, 'c' => 1),

  array('a' => 2, 'b' => 1, 'c' => 3),

  array('a' => 3, 'b' => 2, 'c' => 1),

  array('a' => 3, 'b' => 1, 'c' => 2)

);

?>



To sort an array of objects you would do something like:

Utility::orderBy($objectAry, 'getCreationDate() DESC, getSubOrder() ASC');



This would sort an array of objects that have methods getCreationDate() and getSubOrder().



Here is the function:



<?php

class Utility {

    /*

    * @param array $ary the array we want to sort

    * @param string $clause a string specifying how to sort the array similar to SQL ORDER BY clause

    * @param bool $ascending that default sorts fall back to when no direction is specified

    * @return null

    */

    public static function orderBy(&$ary, $clause, $ascending = true) {

        $clause = str_ireplace('order by', '', $clause);

        $clause = preg_replace('/\s+/', ' ', $clause);

        $keys = explode(',', $clause);

        $dirMap = array('desc' => 1, 'asc' => -1);

        $def = $ascending ? -1 : 1;



        $keyAry = array();

        $dirAry = array();

        foreach($keys as $key) {

            $key = explode(' ', trim($key));

            $keyAry[] = trim($key[0]);

            if(isset($key[1])) {

                $dir = strtolower(trim($key[1]));

                $dirAry[] = $dirMap[$dir] ? $dirMap[$dir] : $def;

            } else {

                $dirAry[] = $def;

            }

        }



        $fnBody = '';

        for($i = count($keyAry) - 1; $i >= 0; $i--) {

            $k = $keyAry[$i];

            $t = $dirAry[$i];

            $f = -1 * $t;

            $aStr = '$a[\''.$k.'\']';

            $bStr = '$b[\''.$k.'\']';

            if(strpos($k, '(') !== false) {

                $aStr = '$a->'.$k;

                $bStr = '$b->'.$k;

            }



            if($fnBody == '') {

                $fnBody .= "if({$aStr} == {$bStr}) { return 0; }\n";

                $fnBody .= "return ({$aStr} < {$bStr}) ? {$t} : {$f};\n";                

            } else {

                $fnBody = "if({$aStr} == {$bStr}) {\n" . $fnBody;

                $fnBody .= "}\n";

                $fnBody .= "return ({$aStr} < {$bStr}) ? {$t} : {$f};\n";

            }

        }



        if($fnBody) {

            $sortFn = create_function('$a,$b', $fnBody);

            usort($ary, $sortFn);        

        }

    }

}

?>

sreid at sea-to-sky dot net

12 years ago


As the manual says, "If two members compare as equal, their order in the sorted array is undefined." This means that the sort used is not "stable" and may change the order of elements that compare equal.



Sometimes you really do need a stable sort. For example, if you sort a list by one field, then sort it again by another field, but don't want to lose the ordering from the previous field. In that case it is better to use usort with a comparison function that takes both fields into account, but if you can't do that then use the function below. It is a merge sort, which is guaranteed O(n*log(n)) complexity, which means it stays reasonably fast even when you use larger lists (unlike bubblesort and insertion sort, which are O(n^2)). 



<?php

function mergesort(&$array, $cmp_function = 'strcmp') {

    // Arrays of size < 2 require no action.

    if (count($array) < 2) return;

    // Split the array in half

    $halfway = count($array) / 2;

    $array1 = array_slice($array, 0, $halfway);

    $array2 = array_slice($array, $halfway);

    // Recurse to sort the two halves

    mergesort($array1, $cmp_function);

    mergesort($array2, $cmp_function);

    // If all of $array1 is <= all of $array2, just append them.

    if (call_user_func($cmp_function, end($array1), $array2[0]) < 1) {

        $array = array_merge($array1, $array2);

        return;

    }

    // Merge the two sorted arrays into a single sorted array

    $array = array();

    $ptr1 = $ptr2 = 0;

    while ($ptr1 < count($array1) && $ptr2 < count($array2)) {

        if (call_user_func($cmp_function, $array1[$ptr1], $array2[$ptr2]) < 1) {

            $array[] = $array1[$ptr1++];

        }

        else {

            $array[] = $array2[$ptr2++];

        }

    }

    // Merge the remainder

    while ($ptr1 < count($array1)) $array[] = $array1[$ptr1++];

    while ($ptr2 < count($array2)) $array[] = $array2[$ptr2++];

    return;

}

?>

Gok6tm

4 years ago


this is a new multisort function for sorting on multiple subfield like it will be in sql : 'ORDER BY field1, field2'

number of sort field is undefined

<?php



$array[] = array('soc' => 3, 'code'=>1);

$array[] = array('soc' => 2, 'code'=>1);

$array[] = array('soc' => 1, 'code'=>1);

$array[] = array('soc' => 1, 'code'=>1);

$array[] = array('soc' => 2, 'code'=>5);

$array[] = array('soc' => 1, 'code'=>2);

$array[] = array('soc' => 3, 'code'=>2);



//usage

print_r(multiSort($array, 'soc', 'code'));



function multiSort() {

    //get args of the function

    $args = func_get_args();

    $c = count($args);

    if ($c < 2) {

        return false;

    }

    //get the array to sort

    $array = array_splice($args, 0, 1);

    $array = $array[0];

    //sort with an anoymous function using args

    usort($array, function($a, $b) use($args) {



        $i = 0;

        $c = count($args);

        $cmp = 0;

        while($cmp == 0 && $i < $c)

        {

            $cmp = strcmp($a[ $args[ $i ] ], $b[ $args[ $i ] ]);

            $i++;

        }



        return $cmp;



    });



    return $array;



}

?>



output:

Array

(

    [0] => Array

        (

            [soc] => 1

            [code] => 1

        )



    [1] => Array

        (

            [soc] => 1

            [code] => 1

        )



    [2] => Array

        (

            [soc] => 1

            [code] => 2

        )



    [3] => Array

        (

            [soc] => 2

            [code] => 1

        )



    [4] => Array

        (

            [soc] => 2

            [code] => 5

        )



    [5] => Array

        (

            [soc] => 3

            [code] => 1

        )



    [6] => Array

        (

            [soc] => 3

            [code] => 2

        )



)

mkr at binarywerks dot dk

13 years ago


If you want to sort an array according to another array acting as a priority list, you can use this function.



<?php

function listcmp($a, $b)

{

  global $order;



  foreach($order as $key => $value)

    {

      if($a==$value)

        {

          return 0;

          break;

        }



      if($b==$value)

        {

          return 1;

          break;

        }

    }

}



$order[0] = "first";

$order[1] = "second";

$order[2] = "third";



$array[0] = "second";

$array[1] = "first";

$array[2] = "third";

$array[3] = "fourth";

$array[4] = "second";

$array[5] = "first";

$array[6] = "second";



usort($array, "listcmp");



print_r($array);

?>

dmhouse at gmail dot com

10 years ago


The easiest way to compare two integers is just to take the second away from the first. For example, say you wanted to sort by an integer property of an object. Your comparison function would look like this:

<?php
function compare_counts($a, $b) {
  return $a->count - $b->count;
}
?>

This works because you don't necessarily have to return -1, 0 or 1, the manual states any integer less than, equal to or greater than 0 is OK.

admin at gosenz dot com

4 years ago


sort multi-dimentional arrays in class with usort

<?php
class ArraySort
{
    private $arr = array();

    public function __construct($arr)
    {
        $this->arr = $arr;
    }

    public function doSort()
    {
        $cmp = function($a, $b)
        {
            //Do Some Comparation
        }
        if(is_array($this->arr))
        {
            usort($this->arr, $cmp);
        }
        return $this->arr;
    }
}
?>

josh at wintelcom dot net

14 years ago


This lets you sort an associative multi-dimensional array by multiple key/field names.  Much similiar to the SQL clause ORDER BY.  Enjoy.



<?php

function cmp ($a, $b) {



    // Populate this array with your values...

    // Below is the SQL equivalent of

    // select * from blah ORDER BY date desc, type asc, name asc



    $vals = array(

        'date' => 'd',

        'type' => 'a',

        'name' => 'a'

    );



    while(list($key, $val) = each($vals)) {



        if($val == "d") {

            if ($a["$key"] > $b["$key"]) {

                return -1;

            }

            if ($a["$key"] < $b["$key"]) {

                return 1;

            }

        }



        if($val == "a") {

            if ($a["$key"] < $b["$key"]) {

                return -1;

            }

            if($a["$key"] > $b["$key"]) {

                return 1;

            }

        }



    }



}

?>

stephen in koto

10 years ago


For using usort inside a method in an object, where the callback sort method is in the same object, this works:



<?php usort($arr_to_sort, array($this, "sort_terms_by_criteria")); ?>



If you wish to keep elements in their original or reverse order if they are the same length, just don't return zero for items that compare the same. Return a 1 or -1, as appropriate.

alex at netflex dot nl

13 years ago


This function will sort on more then one values, test and have fun

<pre>
<?php

  $array[0]['name'] = "a";
  $array[0]['id'] = 3;

  $array[1]['name'] = "a";
  $array[1]['id'] = 2;

  $array[2]['name'] = "a";
  $array[2]['id'] = 5;

  $array[3]['name'] = "b";
  $array[3]['id'] = 8;

  $array[4]['name'] = "b";
  $array[4]['id'] = 1;

  $array[5]['name'] = "b";
  $array[5]['id'] = 0;

  $array[6]['name'] = "c";
  $array[6]['id'] = 5;

  $array[7]['name'] = "c";
  $array[7]['id'] = 7;

  $array[8]['name'] = "c";
  $array[8]['id'] = 3;

  print_r($array);

  $sort_array[0]['name'] = "name";
  $sort_array[0]['sort'] = "ASC";
  $sort_array[0]['case'] = TRUE;

  $sort_array[1]['name'] = "id";
  $sort_array[1]['case'] = FALSE;

  sortx($array, $sort_array);

  print_r($array);

  function sortx(&$array, $sort = array()) {
    $function = '';
    while (list($key) = each($sort)) {
      if (isset($sort[$key]['case'])&&($sort[$key]['case'] == TRUE)) {
        $function .= 'if (strtolower($a["' . $sort[$key]['name'] . '"])<>strtolower($b["' . $sort[$key]['name'] . '"])) { return (strtolower($a["' . $sort[$key]['name'] . '"]) ';
      } else {
        $function .= 'if ($a["' . $sort[$key]['name'] . '"]<>$b["' . $sort[$key]['name'] . '"]) { return ($a["' . $sort[$key]['name'] . '"] ';
      }
      if (isset($sort[$key]['sort'])&&($sort[$key]['sort'] == "DESC")) {
        $function .= '<';
      } else {
        $function .= '>';
      }
      if (isset($sort[$key]['case'])&&($sort[$key]['case'] == TRUE)) {
        $function .= ' strtolower($b["' . $sort[$key]['name'] . '"])) ? 1 : -1; } else';
      } else {
        $function .= ' $b["' . $sort[$key]['name'] . '"]) ? 1 : -1; } else';
      }
    }
    $function .= ' { return 0; }';
    usort($array, create_function('$a, $b', $function));
  }

?>
</pre>

andi_mclean at ntlworld dot com

4 years ago


I needed a sort method that would sort strings but take note of any numbers and would compare them as number. I also want to ignore any non alphanumerical characters.

Eg.
Slot 1 Example
Slot 10 Example
Slot 2 Example

Should infact be
Slot 1 Example
Slot 2 Example
Slot 10 Example

<?php
function sort_with_numbers($a , $b) {
    $a = explode(' ',$a);
    $b = explode(' ',$b);
    $size = min(count($a), count($b));
    for($index =0; $index < $size; ++$index) {
        $a1 = ereg_replace("[^A-Za-z0-9]", "",$a[$index]);
        $b1 = ereg_replace("[^A-Za-z0-9]", "",$b[$index]);
        $equal = 0;
        if (is_numeric($a1) && is_numeric($b1)) {
            $equal = $a1 - $b1;
        } else {
            $equal = strcasecmp($a1,$b1);
        }
        if ($equal < 0) {
            return -1;
        }
        if ($equal > 0) {
            return 1;
        }
    }
    return count($a) - count($b);    
}
?>

Will Shaver

6 years ago


An even better implementation of osort [than my original, posted on 24-AUG-09 (since deleted)], allowing for multiple properties and directions.  With php 5.3.0 sorting by properties of an object becomes MUCH simpler.  Note that this uses anonymous functions / closures. Might find reviewing the php docs on that useful.  Look below for examples for previous version of php.



<?php

function osort(&$array, $props)

{

    if(!is_array($props))

        $props = array($props => true); 

        

    usort($array, function($a, $b) use ($props) {

        foreach($props as $prop => $ascending)

        {

            if($a->$prop != $b->$prop)

            {

                if($ascending)

                    return $a->$prop > $b->$prop ? 1 : -1;

                else

                    return $b->$prop > $a->$prop ? 1 : -1;

            }

        }

        return -1; //if all props equal        

    });    

}

?>



Usage:



<?php

osort($items, array("Color" => true, "Size" => false));

//or

osort($items, "Color");

?>

luke dot semerau at gmail dot com

7 years ago


If you need to use usort with a key in the calling method, I wrote this as a utility:
<?php

function usort_comparison($obj, $method, $key) {
    $usorter = &new Usort($obj, $method, $key);
    return array($usorter, "sort");
}

class Usort {
    function __construct($obj, $method, $key) {
        $this->obj = $obj;
        $this->method = $method;
        $this->key = $key;
    }
    function sort($a, $b) {
        return call_user_func_array(array($this->obj, $this->method), array($a, $b, $this->key));
    }
}

?>

<?php

require_once("util/usort.php");

class Foo {
    $items = array(FooBar(13), FooBar(2));
    public function sorter() {
        usort($this-items, usort_comparison("Foo", "_cmp", "item"));
    }

    public static function _cmp($a, $b, $key) {
         return strcasecmp($a->$key, $b->$key);
    }

}

class FooBar {
    public $item;
    function __construct($val) {
        $this->item = $val;
    }
}

?>

~ simple example... but in the way I need to use it was the key was used in a switch statement to choose the different member of the object to compare against dynamically (as in, sort by x or y or z)

jalil at measat dot org

7 years ago


<?php

/*---------------------------------------------------------

* my own home made easy object sort, which

* i cannot find anywhere on the net

* at all, tut. i can find only complicated ones,

* which brings me a headache.

*

* You can enhance it to return all sorts of error

* conditions if you wish,

* i need nothing but a false return upon failure to sort,

* so that is the only error i have here

*

* Example usage:

*

* INPUT                 -       $objects_array

// an array of objects for sorting



* PARAMETERS    -       property

// the property of the object to be sorted



* OUTPUT                -       $engine

// an engine object created by new,

// with your arrays of objects sorted according to your

// selected property

//( the sorting is done upon sort object creation )

*

* Code Examples

*

* $engine = new objSorter($objects_array);

// sorts on FIRST property -  default



* $engine = new objSorter($objects_array,'property');

// sort on ANY specific property

*--------------------------------------------------------*/



class objSorter 

{

var $property;

var $sorted;



    function ObjSorter($objects_array,$property=null) 

        {

            $sample    = $objects_array[0];

            $vars    = get_object_vars($sample);



        if (isset($property))

            {

            if (isset($sample->$property)) 

// make sure requested property is correct for the object

                {    

                $this->property = $property;

                usort($objects_array, array($this,'_compare'));

                }

            else

                {    

                $this->sorted    = false;

                return;    

                }

            }

        else

            {    

                list($property,$var)     = each($sample);

                $this->property         = $property;

                usort($objects_array, array($this,'_compare'));

            }



        $this->sorted    = ($objects_array);

        }



    function _compare($apple, $orange) 

        {

        $property    = $this->property;

        if ($apple->$property == $orange->$property) return 0;

        return ($apple->$property < $orange->$property) ? -1 : 1;

        }

} // end class

?>



USAGE EXAMPLE

DUMP ORIGINAL

user Object ( [name] => Yunihe Jopoba [age] => 27 [richness] => â‚¬ 899,970 )

user Object ( [name] => Janirevi Fakejorumoa [age] => 19 [richness] => â‚¬ 219,078 )

user Object ( [name] => Korejowi Mezede [age] => 95 [richness] => â‚¬ 3,272 )

user Object ( [name] => Nugoaivu Jongyi [age] => 84 [richness] => â‚¬ 94,853 )

user Object ( [name] => Cepomase Buaesukoyua [age] => 32 [richness] => â‚¬ 677,180 )

user Object ( [name] => Vejosehona Auva [age] => 20 [richness] => â‚¬ 144,540 )

user Object ( [name] => Fewame Wojuvuzo [age] => 69 [richness] => â‚¬ 198,231 )

user Object ( [name] => Risuku Zagedobu [age] => 48 [richness] => â‚¬ 763,860 )

user Object ( [name] => Fazurada Aayu [age] => 16 [richness] => â‚¬ 302,352 )



SORTED by age



<?php

$objects                = new ObjSorter($objects_array,'age');

if ($objects->sorted)

{

$objects_array  = $objects->sorted;

foreach ($objects_array as $key=>$object) { print_r($object); echo "<br />"; }

}

?>



user Object ( [name] => Fazurada Aayu [age] => 16 [richness] => â‚¬ 302,352 )

user Object ( [name] => Janirevi Fakejorumoa [age] => 19 [richness] => â‚¬ 219,078 )

user Object ( [name] => Vejosehona Auva [age] => 20 [richness] => â‚¬ 144,540 )

user Object ( [name] => Yunihe Jopoba [age] => 27 [richness] => â‚¬ 899,970 )

user Object ( [name] => Cepomase Buaesukoyua [age] => 32 [richness] => â‚¬ 677,180 )

user Object ( [name] => Risuku Zagedobu [age] => 48 [richness] => â‚¬ 763,860 )

user Object ( [name] => Fewame Wojuvuzo [age] => 69 [richness] => â‚¬ 198,231 )

user Object ( [name] => Nugoaivu Jongyi [age] => 84 [richness] => â‚¬ 94,853 )

user Object ( [name] => Korejowi Mezede [age] => 95 [richness] => â‚¬ 3,272 )



SORTED by richness



<?php

$objects                = new ObjSorter($objects_array,'richness');

if ($objects->sorted)

{

$objects_array  = $objects->sorted;

foreach ($objects_array as $key=>$object) { print_r($object); echo "<br />"; }

}

?>



user Object ( [name] => Vejosehona Auva [age] => 20 [richness] => â‚¬ 144,540 )

user Object ( [name] => Fewame Wojuvuzo [age] => 69 [richness] => â‚¬ 198,231 )

user Object ( [name] => Janirevi Fakejorumoa [age] => 19 [richness] => â‚¬ 219,078 )

user Object ( [name] => Korejowi Mezede [age] => 95 [richness] => â‚¬ 3,272 )

user Object ( [name] => Fazurada Aayu [age] => 16 [richness] => â‚¬ 302,352 )

user Object ( [name] => Cepomase Buaesukoyua [age] => 32 [richness] => â‚¬ 677,180 )

user Object ( [name] => Risuku Zagedobu [age] => 48 [richness] => â‚¬ 763,860 )

user Object ( [name] => Yunihe Jopoba [age] => 27 [richness] => â‚¬ 899,970 )

user Object ( [name] => Nugoaivu Jongyi [age] => 84 [richness] => â‚¬ 94,853 )



Simulated wrong property request ( dumb property )



<?php

$objects                = new ObjSorter($objects_array,'dumb property');

if ($objects->sorted)

{

$objects_array  = $objects->sorted;

foreach ($objects_array as $key=>$object) { print_r($object); echo "<br />"; }

}

else echo 'DUMB ERROR';

?>



DUMB ERROR

drorasta

7 years ago


Here's how you can usort() a multidimensional array (like in example #2 above) within a class:



<?php usort($myArray, array("className", "cmp")); ?>

Sid_M

8 years ago


The sample function for having the sort function be a class method has a comment identifying the sorting function as static, however the function does not have the static keyword. In PHP 5 (at least as configured on my server), usort will fail, identifying the method as non-static. Preceding the function keyword with the static keyword fixed the problem.

Gerald Schneider

2 years ago


usort returns null when the sorting function is not (yet) defined. The function has to be defined before usort is called, afterwards doesn't work.

bcsj

4 years ago


Sorting a multidimensional array by a subkey seem to be one of the bigger challenges when using usort. At least if one want the key to be dynamic. For anyone interested this code seemed to work rather well for me:

<?php

usort($array,array(new cmp($key), "cmp__"));

class cmp {
    var $key;
    function __construct($key) {
        $this->key = $key;
    }
    
    function cmp__($a,$b) {
        $key = $this->key;
        if ($a[$key] == $b[$key]) return 0;
        return (($a[$key] > $b[$key]) ? 1 : -1);
    }
}

?>

guenther dot stadler at gmx dot net

11 years ago


Just something i stumbled about right now:
If the array consists of just one elemtent, the user-function is not called at all.

Although this surely makes sense, think of it if you want to use your order-function for adding extra data to your arrays...

skrebbel at operamail dot com

13 years ago


here's another recursive multisort, however a clean and fast one that is class-based (but works as well outside classes) and does not uglify your global namespace at all. note that strnatcmp is used, but one could use something else of course.



btw, for arrays in which the rows/columns are 'swapped', use array_multisort().



<?php

class Banana {

    var $aData;//the array we want to sort.

    var $aSortkeys;//the order in which we want the array to be sorted.

    function _sortcmp($a, $b, $i=0) {

        $r = strnatcmp($a[$this->aSortkeys[$i]],$b[$this->aSortkeys[$i]]);

        if($r==0) {

            $i++;

            if ($this->aSortkeys[$i]) $r = $this->_sortcmp($a, $b, $i+1);

        }

        return $r;

    }

    function sort() {

        if(count($this->aSortkeys)) {

            usort($this->aData,array($this,"_sortcmp"));

        }

    }

}

$B = new Banana;

$B->aData = array(

    array("name" => "hank", "headsize" => "big", "age" => 32),

    array("name" => "frank", "headsize" => "huge", "age" => 36)

);

$B->aSortkeys = array("age","name");

$B->sort();



?>

sorry for the ugly indenting, but i couldn't get it any better in this note adder thing.

prozac at iguanasoft dot com

13 years ago


Here is a simple example of converting a timestamp date("U") into a date. This sorts by that day and then by string value alphabetically.



I hope it saves someone some time... Happy PHP'in!



<?php

//data to sort

$shared[0]["page_id"] = "2025731470";

$shared[1]["page_id"] = "2025731450";

$shared[2]["page_id"] = "1025731456";

$shared[3]["page_id"] = "1025731460";

$shared[0]["username"] = "larry";

$shared[1]["username"] = "alvin";

$shared[2]["username"] = "garth";

$shared[3]["username"] = "harvy";



//function to convert timestamp to date

function convert_timestamp($timestamp){

    $limit=date("U");

    $limiting=$timestamp-$limit;

    return date ("Ymd", mktime (0,0,$limiting));

}

//comparison function

function cmp ($a, $b) {

    $l=convert_timestamp($a["page_id"]);

    $k=convert_timestamp($b["page_id"]);

    if($k==$l){

        return strcmp($a["username"], $b["username"]);

    }else{

        return strcmp($k, $l);

    }

}



//sort array

usort($shared, "cmp");



//display sorted info

while (list ($key, $value) = each ($shared)) {

    echo "\$shared[$key]: ";

    echo $value["page_id"];

    echo " username: ";

    echo $value["username"];

    echo "<break_tag>";

}

?>



This will output:

$shared[0]: 2025731450   username: alvin

$shared[1]: 2025731470   username: larry

$shared[2]: 1025731456   username: garth

$shared[3]: 1025731460   username: harvy

xaguilars at gmail dot com

5 years ago


I'd like to share with the community my function for sorting an array of arrays or objects containing associative data. This could be used, for example, with a MySQL result.

<?php
function sort_by($field, &$arr, $sorting=SORT_ASC, $case_insensitive=true){
    if(is_array($arr) && (count($arr)>0) && ( ( is_array($arr[0]) && isset($arr[0][$field]) ) || ( is_object($arr[0]) && isset($arr[0]->$field) ) ) ){
        if($case_insensitive==true) $strcmp_fn = "strnatcasecmp";
        else $strcmp_fn = "strnatcmp";

        if($sorting==SORT_ASC){
            $fn = create_function('$a,$b', '
                if(is_object($a) && is_object($b)){
                    return '.$strcmp_fn.'($a->'.$field.', $b->'.$field.');
                }else if(is_array($a) && is_array($b)){
                    return '.$strcmp_fn.'($a["'.$field.'"], $b["'.$field.'"]);
                }else return 0;
            ');
        }else{
            $fn = create_function('$a,$b', '
                if(is_object($a) && is_object($b)){
                    return '.$strcmp_fn.'($b->'.$field.', $a->'.$field.');
                }else if(is_array($a) && is_array($b)){
                    return '.$strcmp_fn.'($b["'.$field.'"], $a["'.$field.'"]);
                }else return 0;
            ');
        }
        usort($arr, $fn);
        return true;
    }else{
        return false;
    }
}
?>

Anonymous

7 years ago


To sort reliably on more than one "column" in database-style arrays, handle this within your cmp function where the first field to be sorted returns 0:

<?php

function cmp($a, $b){
    
 if($a[field_1] == $b[field_1]){

  if($a[field_2] == $b[field_2]){

   return 0;

  }

  elseif($a[field_2] > $b[field_2]){

   return -1;

  }

  elseif($a[field_2] < $b[field_2]){

   return 1;

  }

 }

 elseif($a[field_1] > $b[field_1]){

  return -1;

 }

 elseif($a[field_1] < $b[field_1]){

  return 1;

 }

}

?>

Sorting by doing multiple passes does not seem to be reliable.

webmaster at zeroweb dot org

12 years ago


Needed a quick, fairly uncluttered way of sorting an array of objects by a certain object attribute, so here's what I came up with. Uses one global array and usort(). Also accepts an optional sort direction argument (CSORT_ASC = sort ascending, CSORT_DESC = sort descending). Use it like this:



(assuming $myarray is your array, "index" is the attribute you want to sort by, and you want to sort in descending order)



      csort($myarray, "index", CSORT_DESC);



Hope this is of use to someone. Probably a better way to pull this off, but this works alright.



<?php

define("CSORT_ASC",     1);

define("CSORT_DESC",     -1);



function csort_cmp(&$a, &$b)

{

    global $csort_cmp;



    if ($a->$csort_cmp['key'] > $b->$csort_cmp['key'])

        return $csort_cmp['direction'];



    if ($a->$csort_cmp['key'] < $b->$csort_cmp['key'])

        return -1 * $csort_cmp['direction'];



    return 0;

}



function csort(&$a, $k, $sort_direction=CSORT_ASC)

{

    global $csort_cmp;



    $csort_cmp = array(

        'key'           => $k,

        'direction'     => $sort_direction

    );



    usort($a, "csort_cmp");



    unset($csort_cmp);

}

?>

Nsisodia91 at gmail dot com

2 months ago


You can also sort multi-dimensional array for multiple values like as

<?php 
$arr = [
    [
        "name"=> "Sally",
        "nick_name"=> "sal",
        "availability"=> "0",
        "is_fav"=> "0"
    ],
    [
        "name"=> "David",
        "nick_name"=> "dav07",
        "availability"=> "0",
        "is_fav"=> "1"
    ],
    [
        "name"=> "Zen",
        "nick_name"=> "zen",
        "availability"=> "1",
        "is_fav"=> "0"
    ],
    [
        "name"=> "Jackson",
        "nick_name"=> "jack",
        "availability"=> "1",
        "is_fav"=> "1"
    ],
    [
        "name"=> "Rohit",
        "nick_name"=> "rod",
        "availability"=> "0",
        "is_fav"=> "0"
    ],

];

usort($arr,function($a,$b){
    $c = $b['is_fav'] - $a['is_fav'];
    $c .= $b['availability'] - $a['availability'];
    $c .= strcmp($a['nick_name'],$b['nick_name']);
    return $c;
});

print_r($arr);
?>

Output:

Array
(
    [0] => Array
        (
            [name] => Jackson
            [nick_name] => jack
            [availability] => 1
            [is_fav] => 1
        )

    [1] => Array
        (
            [name] => David
            [nick_name] => dav07
            [availability] => 0
            [is_fav] => 1
        )

    [2] => Array
        (
            [name] => Zen
            [nick_name] => zen
            [availability] => 1
            [is_fav] => 0
        )

    [3] => Array
        (
            [name] => Rohit
            [nick_name] => rod
            [availability] => 0
            [is_fav] => 0
        )

    [4] => Array
        (
            [name] => Sally
            [nick_name] => sal
            [availability] => 0
            [is_fav] => 0
        )

)

bob at thecaverlys dot net

1 year ago


Below is a variation on Example #4 that implements a multi-key natural sort on an associative array and can be called in such a way as to allow reversing the sort order and/or making the comparison case insensitive on a key by key basis.

Test code is included in the file – run it from the command line with: php sortUtils.php

<?php
/**
 *    sortUtils.php
*/

/**
 *    mknatsort() - Multi-Key Natural Sort for associative arrays
 *
 *    Uses the usort() function to perform a natural sort on a multi-dimensional
 *    array on multiple keys. Optionally specifying the sort order for each key
 *    and/or ignoring the case for each key value.
 *
 *    @param array $data_array The array to be sorted.
 *    @param mixed $keys The list of keys to be sorted by. This may be a single
 *        key or an array of keys
 *    @param boolean $reverse Specify whether or not to reverse the sort order. If
 *        there are multiple keys then $reverse may be an array of booleans - one
 *        per key.
 *    @param boolean $ignorecase Specify whether or not to ignore the case when
 *        comparing key values.reverse the sort order. If there are multiple keys
 *        then $ignorecase may be an array of booleans - one per key.
*/
function mknatsort ( &$data_array, $keys, $reverse=false, $ignorecase=false ) {
    // make sure $keys is an array
    if (!is_array($keys)) $keys = array($keys);
    usort($data_array, sortcompare($keys, $reverse, $ignorecase) );
}

function sortcompare($keys, $reverse=false, $ignorecase=false) {
    return function ($a, $b) use ($keys, $reverse, $ignorecase) {
        $cnt=0;
        // check each key in the order specified
        foreach ( $keys as $key ) {
            // check the value for ignorecase and do natural compare accordingly
            $ignore = is_array($ignorecase) ? $ignorecase[$cnt] : $ignorecase;
            $result = $ignore ? strnatcasecmp ($a[$key], $b[$key]) : strnatcmp($a[$key], $b[$key]);
            // check the value for reverse and reverse the sort order accordingly
            $revcmp = is_array($reverse) ? $reverse[$cnt] : $reverse;
            $result = $revcmp ? ($result * -1) : $result;
            // the first key that results in a non-zero comparison determines
            // the order of the elements
            if ( $result != 0 ) break;
            $cnt++;
        }
        return $result;
    };
} // end sortcompare()

// test code that will be skipped if this is included in the web environment
// test with: php sortUtils.php from the command line
$sapi_type = php_sapi_name();
if (substr($sapi_type, 0, 3) == 'cli') {

    // the following shows several examples of usage and the resulting output.
    $test[] = array('Status'=>'In Progress', 'comment'=>'This looks good.', 'user_name'=>'John Doe', 'date_modified'=>'06/13/2014 11:20 AM', 'role'=>'Senior Account Manager');
    $test[] = array('Status'=>'In Progress', 'comment'=>'This looks good, please approve.', 'user_name'=>'John Doe', 'date_modified'=>'06/13/2014 11:19 AM', 'role'=>'Account Manager');
    $test[] = array('Status'=>'In Progress', 'comment'=>'This looks good.', 'user_name'=>'Jane Smith', 'date_modified'=>'06/13/2014 11:19 AM', 'role'=>'Senior Account Manager');
    $test[] = array('Status'=>'Returned', 'comment'=>'There is not enough informartion.  Please add the following.', 'user_name'=>'John Doe', 'date_modified'=>'06/13/2014 11:15 AM', 'role'=>'Account Manager');
    $test[] = array('Status'=>'In Progress', 'comment'=>'I am currently reviewing this.', 'user_name'=>'John Doe', 'date_modified'=>'06/13/2014 11:14 AM', 'role'=>'Account Manager');
    echo "Original array: ";
    print_r($test);

    echo "Sorted on date_modified: ";
    mknatsort($test, array('date_modified') );
    print_r($test);

    echo "Sorted on role(reversed) & date_modified: ";
    mknatsort($test, array('role','date_modified'),array(true,false) );
    print_r($test);

    echo "Sorted on role & date_modified(reversed): ";
    mknatsort($test, array('role','date_modified'),array(false,true) );
    print_r($test);
}

?>

fmaz008 at gmail dot com

5 years ago


This comment is just to help backward compatibility.

I needed to have a foreach loop using reference just before using the usort function on the same array that was used in the foreach.

Like this:
<?php
public function sortByTitle()
{
        if(empty($this->_arrSubCat))
            return false;
        
        foreach($this->_arrSubCat as &$cat)
            $cat->sortByTitle();
        
        usort($this->_arrSubCat, 'strcasecmp');
}
?>

I had this strange bug where the last object of the $this->_arrSubCat array before the sort was alway replaced/overwrited with his string value.

On my machine (PHP 5.3), I had no problem, but when I placed the code on another server, my code crashed with a fatal error (Because I was using a string as an object later in the code)

The solution I found is really simple, and avoid the array to have a reference declared in memory while running the sort function. Just add an unset($cat):

<?php
public function sortByTitle()
{
        if(empty($this->_arrSubCat))
            return false;
        
        foreach($this->_arrSubCat as &$cat)
            $cat->sortByTitle();
        
        unset($cat); //No more problem because of the foreach &cat reference.    
        usort($this->_arrSubCat, 'strcasecmp');
}
?>

It took me an hour an a half to locate the bug, hope it will save someone some time !

Hayley Watson

3 years ago


As the documentation says, the comparison function needs to return an integer that is either "less than, equal to, or greater than zero". There is no requirement to restrict the value returned to -1, 0, 1.

<?php
usort($array, function($a, $b) {
    if($a->integer_property > $b->integer_property) {
        return 1;
    }
    elseif($a->integer_property < $b->integer_property) {
        return -1;
    }
    else {
        return 0;
    }
});
?>

can be simplified to

<?php
usort($array, function($a, $b) {
    return $a->integer_property - $b->integer_property;
});
?>

This of course applies to any comparison function that calculates an integer "score" for each of its arguments to decide which is "greater".

maarten at xel dot nl

6 years ago


If you ever have to sort a collection of objects on something like a string (name) present in every object, but want to keep the array of objects intact you might find this useful:



<?php

function naturalSortObjectArray($objectArray) {

        function naturalSortByName($a, $b) {

            return strnatcmp($a->name, $b->name);

        }

        usort($objectArray, "naturalSortByName");

        return $objectArray;

}

?>

huskyr at gmail dot com

6 years ago


Remember that functions inside of functions will become part of the global scope too. So, something like:

<?php
    function foo($array) {
        function compare($a,$b) {
            return $a < $b;
        }
        usort($array, "compare");
        return $array;
    }
    
    function bar($array) {
        function compare($a,$b) {
            return $a > $b;
        }
        usort($array, "compare");
        return $array;
    }
    
    foo($something);
    bar($something_else);
?>
        
Will result in a fatal error because you're redeclaring 'compare'. This could be a little strange, e.g. for JavaScript programmers who expect functions in functions to become private outside of the parent scope.

kostya dot develop at gmail dot com

3 months ago


Now, in php 7, we can use the spaceship operator. For example lest sort array of words from element string length:

<?php
$sampleArray = ['one', 'two', free', 'fore', 'five'];

usort($sampleArray, function($a, $b) {
      return strlen($a) <=> strlen($b);
});

Ariz Jacinto

7 years ago


Here's how to use usort() within a class using a static function as a callback (using the example above):

<?php

class MyObj {
    var $name;

    function SampleObj($name){
        $this->name = $name;

        usort($this->name, array(&$this, "compareValues"));

    }

    static function compareValues($a, $b){
        $al = strtolower($a->name);
        $bl = strtolower($b->name);
        if ($al == $bl) {
            return 0;
        }
        return ($al > $bl) ? +1 : -1;
    }
}

?>

me at evertpot dot com

9 months ago


I see many people here (including the official examples) write their callbacks rather clumsily like this:

<?php
function($a, $b) {
  if ($a === $b) {
    return 0;
  } elseif ($a < $b) {
    return -1;  
  } else {
    return 1;
  }
}
?>

Or if they are a bit more clever:

<?php
function($a, $b) {

  if ($a === $b) {
    return 0;
  } else {
    return $a < $b ? -1 : 1;
  }
}
?>

But this can by simplified further to:

<?php
function($a, $b) {
  return $a - $b;
}
?>

Lea Hayes

4 years ago


<?php

/**

 * Sort array of objects by field.

 *

 * @param array $objects Array of objects to sort.

 * @param string $on Name of field.

 * @param string $order (ASC|DESC)

 */

function sort_on_field(&$objects, $on, $order = 'ASC') {

    $comparer = ($order === 'DESC')

        ? "return -strcmp(\$a->{$on},\$b->{$on});"

        : "return strcmp(\$a->{$on},\$b->{$on});";

    usort($objects, create_function('$a,$b', $comparer));

}

?>

phil at lavin dot me dot uk

5 years ago


strcmp (or strcasecmp) can be used as a callback function for usort. It will cast your comparison values to string. Thus, you can implement a __toString() method into your classes and use usort without creating a callback function:

<?php
class Foo {
   private $a;
   private $b;

   public function __construct($a, $b) {
      $this->a = $a;
      $this->b = $b;
   }

   public function __toString() {
      return (string)$this->a;
   }
}

$foo = array(new Foo('t', 'b'), new Foo('a', 'c'), new Foo('g', 'd'));

print_r($foo);

usort($foo, 'strcasecmp');

print_r($foo);
?>

hexarobi at gmail dot com

3 years ago


Needed to sort an array of objects based on multiple properties. (ie: Group, then Last Name, then First Name) Doing this in multiple usorts fails because the second usort ends up shuffling the results of the previous usort because order is undefined when criteria are equal. Ended up writing a function that builds a comparison operator by nesting ternary operators for each field, then using that function in usort(). Hopefully it's of use to someone else.



<?php

/*

 * Sorts an array of objects by a list of properties.

 * Each property can have the following options:

 *   'property' can be either a public variable or a method().

 *   'order' can be ASC or DESC

 *   'comparer' can be string, number, or date

 * 

 * Example:

 * sortObjectsByProperties($objects, array(

 *       array('property'=>'getPrice()', order=>'ASC', 'comparer'=>'number'),

 *       array('property'=>'getName()', order=>'DESC', 'comparer'=>'string'),

 *       array('property'=>'created_date', order=>'ASC', 'comparer'=>'date'),

 *       array('property'=>'id', order=>'ASC', 'comparer'=>'number'),

 *   ));

 * 

 * @author Tyler Chamberlain

 */

function sortObjectsByProperties(&$objects, $fields) {

        $comparerFunctionString = "";

        foreach ($fields as $field) {

            if ($field['comparer'] == 'number') {

                $comparerFunction = "(\$a->{$field['property']} == \$b->{$field['property']} ? 0 : (\$a->{$field['property']} > \$b->{$field['property']} ? 1 : -1))";

            } elseif ($field['comparer'] == 'date') {

                $comparerFunction = "(strtotime(\$a->{$field['property']}) > strtotime(\$b->{$field['property']}) ? 1 : -1)";

            } else {

                $comparerFunction = "strcasecmp(\$a->{$field['property']},\$b->{$field['property']})";

            }

            if ($field['order'] === 'DESC') { $comparerFunction = "-".$comparerFunction; }

            $comparerFunctionString .= "$comparerFunction != 0 ? $comparerFunction : (";

        }

        $comparer = "return ($comparerFunctionString 0 )".str_repeat(")", sizeof($fields)).";";

        usort($objects, create_function('$a,$b', $comparer)); 

}

?>

sean at NOSPAM dot orwd dot com

10 years ago


In order to get a proper text sorting I have changed the arfsort() function submitted by jonathan(at)inetz(dot)com.

The one line I have changed is:

<?php
$strc = strcmp( $a[$f], $b[$f] );
?>

to

<?php
$strc = strcmp( strtolower($a[$f]), strtolower($b[$f]) );
?>

It can now sort correctly for alphabetization.  Capital letters where getting in the way.

Sean

Jeremy Swinborne

10 years ago


When I query a DB I usually put my record set inside of a multi-dimentional array.  I finally wrote a program that will allow you to sort your record set by column after you put it in an array.



<?php

$test = array();

$test[0]['name'] = 'jeremy';

$test[0]['email'] = 'lala@example.com';

$test[0]['phone'] = '123-123-1234';

$test[0]['trick'] = 'mezopia';



$test[1]['name'] = 'Amanda';

$test[1]['email'] = 'hot@example.com';

$test[1]['phone'] = '123-123-1235';

$test[1]['trick'] = 'youarecool';



$test[2]['name'] = 'john';

$test[2]['email'] = 'wowee@example.com';

$test[2]['phone'] = '123-123-3333';

$test[2]['trick'] = 'goneinanhour';



print_r(columnSort($test, 'name'));



function columnSort($unsorted, $column) {

    $sorted = $unsorted;

    for ($i=0; $i < sizeof($sorted)-1; $i++) {

      for ($j=0; $j<sizeof($sorted)-1-$i; $j++)

        if ($sorted[$j][$column] > $sorted[$j+1][$column]) {

          $tmp = $sorted[$j];

          $sorted[$j] = $sorted[$j+1];

          $sorted[$j+1] = $tmp;

      }

    }

    return $sorted;

}

?>

Jian Wu

3 years ago


The usort function actually moves $b up when the callback function returns both 0 and 1.  If you want to preserve the original order in the array, return 1 when $a == $b instead of 0.  Try this code below to see how usort alters the order of the original array when all values are the same.



<?php

class TestObj {

    private $name;

    private $id;



    function TestObj($name, $id) {

        $this->name = $name;

        $this->id = $id;

    }



    static function cmp_obj($a, $b) {

        $al = strtolower($a->name);

        $bl = strtolower($b->name);

        if ($al == $bl) {

            return 0; // return 1 if you don't want $b to go in front of $a

        }

        return ($al > $bl) ? +1 : -1;

    }

}



$a[] = new TestObj("a", 1);

$a[] = new TestObj("a", 2);

$a[] = new TestObj("a", 3);



var_dump($a);

usort($a, array("TestObj", "cmp_obj"));

var_dump($a);

?>

Raveler at telenet dot be

11 years ago


The array_alternate_multisort function written by robert below doesn't work. There are several bugs in the code and it doesn't work when sorting by multiple keys because the order of the first key isn't taken into account when sorting by the second key and so on. Also, because robert uses strcasecmp the algorithm doesn't work properly with floats or other variable types. Here's the improved version:

<?php
    function SortArray() {
        $arguments = func_get_args();
        $array = $arguments[0];
        $code = '';
        for ($c = 1; $c < count($arguments); $c += 2) {
            if (in_array($arguments[$c + 1], array("ASC", "DESC"))) {
                $code .= 'if ($a["'.$arguments[$c].'"] != $b["'.$arguments[$c].'"]) {';
                if ($arguments[$c + 1] == "ASC") {
                    $code .= 'return ($a["'.$arguments[$c].'"] < $b["'.$arguments[$c].'"] ? -1 : 1); }';
                }
                else {
                    $code .= 'return ($a["'.$arguments[$c].'"] < $b["'.$arguments[$c].'"] ? 1 : -1); }';
                }
            }
        }
        $code .= 'return 0;';
        $compare = create_function('$a,$b', $code);
        usort($array, $compare);
        return $array;
    }
?>

masonswolf+ignorethispart at gmail dot com

4 years ago


[The second version of a function I wrote], just a little cleaner to use, since the usort call is now folded into the custom 'usortByArrayKey' function.



Seems like this is a popular problem - sorting an array of arrays by the keys of sub-arrays, so I'll go ahead and throw in an approach I haven't seen anyone mention yet. It only works since PHP 5.3 because that's when anonymous functions got added to the language. 



<?php 

function usortByArrayKey(&$array, $key, $asc=SORT_ASC) { 

    $sort_flags = array(SORT_ASC, SORT_DESC); 

    if(!in_array($asc, $sort_flags)) throw new InvalidArgumentException('sort flag only accepts SORT_ASC or SORT_DESC'); 

    $cmp = function(array $a, array $b) use ($key, $asc, $sort_flags) { 

        if(!is_array($key)) { //just one key and sort direction 

            if(!isset($a[$key]) || !isset($b[$key])) { 

                throw new Exception('attempting to sort on non-existent keys'); 

            } 

            if($a[$key] == $b[$key]) return 0; 

            return ($asc==SORT_ASC xor $a[$key] < $b[$key]) ? 1 : -1; 

        } else { //using multiple keys for sort and sub-sort 

            foreach($key as $sub_key => $sub_asc) { 

                //array can come as 'sort_key'=>SORT_ASC|SORT_DESC or just 'sort_key', so need to detect which 

                if(!in_array($sub_asc, $sort_flags)) { $sub_key = $sub_asc; $sub_asc = $asc; } 

                //just like above, except 'continue' in place of return 0 

                if(!isset($a[$sub_key]) || !isset($b[$sub_key])) { 

                    throw new Exception('attempting to sort on non-existent keys'); 

                } 

                if($a[$sub_key] == $b[$sub_key]) continue; 

                return ($sub_asc==SORT_ASC xor $a[$sub_key] < $b[$sub_key]) ? 1 : -1; 

            } 

            return 0; 

        } 

    };

    usort($array, $cmp);

}; 

?>



Examples: 

1) Sort a multi-dimensional array by a single key, from least to greatest: 

    usortByArrayKey($resultset, 'order_id'); 



2) Sort a multi-dimensional array by a single key, from greatest to least: 

    usortByArrayKey($resultset, 'purchase_amount', SORT_DESC); 



3) Sort a multi-dimensional array first by one key, but then by a different key when the first one is equal, both from least to greatest: 

    usortByArrayKey($resultset, array('product_id', 'price')); 



4) Sort a multi-dimensional array by two different keys from least to greatest, and then a third from greatest to least if the first two keys map to the equal values: 

    usortByArrayKey($resultset, array('product_id', 'customer_id', 'date'=>SORT_DESC)); 



5) Sort a multi-dimensional array by multiple keys, all from greatest to least: 

    usortByArrayKey($resultset, array('product_id', 'price'), SORT_DESC);



One word of caution, since SORT_ASC and SORT_DESC have actual int values of 4 and 3, respectively, if you need to sort a multi-dimensional array by keys 3 or 4, and you're using an array to pass in your keys, you MUST specify your sort flags (e.g. array(3 => SORT_ASC,...)) to prevent unexpected behavior, instead of relying on the function's second parameter as your default sort flag.

Tim

9 years ago


If you want to sort an array of strings by the length of its values, you can write a better cmp-function than manually comparing string lengths with if-statements. Unfortunately, I see this bad technique in other people's code. I prefer using this:

<?php
function length_cmp( $a, $b ) {
    return strlen($a)-strlen($b) ;
}
?>

This function sorts the array in ascending order. If you want to sort descending, simply swap $a and $b either in the parameters or in the subtraction.

-Tim

nicolas dot demarque at gmail dot com

6 years ago


Another way to compare object is to have a compare static function in the class with reccursion ability and have globals or static variables who save the state of comparison, and the order.

It could be a good idea to have a variable with comparison functions name (with the sorting : numeric, alphanumeric, inverse).

<?php
interface Comparable{static function compare($a, $b);}
class myObj implements Comparable{
        var $var1; var $var2; var $var3;
        function __construct($v1, $v2, $v3){
                $this->var1=$v1; $this->var2=$v2; $this->var3=$v3;
        }
        public function __toString() {
                return "v1 ".$this->var1." v2 ".$this->var2." v3 ".$this->var3;
        }
        static function compare($a, $b){
                $sort=$GLOBALS['sorts'][$GLOBALS['sort']];
                echo "$sort\n";
                if($a->$sort == $b->$sort){
                        if($GLOBALS['sorts'][$GLOBALS['sort']+1]){
                                $GLOBALS['sort']++;
                                $res=  call_user_func(array('myObj', 'compare'), $a, $b);
                                $GLOBALS['sort']=0; return $res;
                        }
                        $GLOBALS['sort']=0; return 0;
                }
                $GLOBALS['sort']=0;
                if($a->$sort > $b->$sort)
                        return 1;
                return -1;
        }
}

$objects = array(new myObj("1", "2", "3"), new myObj("2", "2", "2"), new myObj("1", "3", "4"));

/* Tests */
$sorts=Array('var1', 'var2', 'var3'); $sort = 0; usort($objects, array('myObj', 'compare')); echo ("var1 var2 var3\n"); foreach($objects as $o)echo $o."\n";
$sorts=Array('var2', 'var3', 'var1'); $sort = 0; usort($objects, array('myObj', 'compare')); echo ("\nvar2 var3 var1\n"); foreach($objects as $o)echo $o."\n";
$sorts=Array('var2', 'var1', 'var3'); $sort = 0; usort($objects, array('myObj', 'compare')); echo ("\nvar2 var1 var3\n"); foreach($objects as $o)echo $o."\n";

?>

me at perochak dot com

2 years ago


If you want to sort the time based array, then this will be helpfull.

function timesort($array){
            usort($array, function($a, $b)
            {
                $a=strtotime($a);
                $b=strtotime($b);
                
                if ($a == $b)
                {
                    return 0;
                }
                else if ($a < $b)
                {
                    return -1;
                }
                else {
                    return 1;
                }
            });
}

Input:

$time_array=Array
(
    [1] => 10:00AM
    [2] => 09:00AM
    [3] => 02:00PM
    [4] => 11:00AM
)

Output: 
print_r(timesort($time_array));
Array
(
    [0] => 09:00AM
    [1] => 10:00AM
    [2] => 11:00AM
    [3] => 02:00PM
)

Paul Geraghty foofoonet at the G Mall

6 years ago


For anyone else sorting mixed RSS feeds in date order, here's an example of the perhaps not so obvious way of calling a method from the same class using usort():



<?php

class MyAggregator {



  static function cmp_pubdate( $a, $b ) {

    $a_t = strtotime( $a['pubdate'] ) ;

    $b_t = strtotime( $b['pubdate'] ) ;



    if( $a_t == $b_t ) return 0 ;

    return ($a_t > $b_t ) ? -1 : 1;

  }



// assemble arrays for display in date order

  function all_documents(){

    $all_data  = array_merge ( 

    $this->upcoming(), $this->past() ) ; 



// Use within its own class using the $this syntax so:

    usort( $all_data, array( $this , "cmp_pubdate" ) ) ;



  return $all_data ;

  }

}

?>



As previously said, use as a static function in other parts of your code:



<?php usort ( $a, array( "MyAggregator", "cmp_pubdate" ) ) ; ?>

sydney at totoche dot org

10 years ago


Instead of doing  :



<?php $strc = strcmp( strtolower($a[$f]), strtolower($b[$f]) ); ?>



you could do this : 



<?php $strc = strcasecmp( $a[$f], $b[$f] ); ?>



which is more efficient and is does case insensitive comparison according to the current locale.

franky at iname dot com

14 years ago


For sort multi-array by specific index



<?php

function cmp ($a, $b)

{   

 global $w_o;

 if ($a[$w_o] == $b[$w_o]) return 0;

 return ($a[$w_o] < $b[$w_o]) ? -1 : 1;

}

# the index is the second element of 

# each row



$w_o =1;

usort($my_arry_info,"cmp");

?>

derek at luddite dot net

15 years ago


Needed a date sort and I didn't know if one was available so I wrote one. Maybe it'll help someone:



<?php

function DateSort($a,$b,$d="-") {

    if ($a == $b) {

        return 0;

    } else {  //Convert into dates and compare

        list($am,$ad,$ay)=split($d,$a);

        list($bm,$bd,$by)=split($d,$b);

        if (mktime(0,0,0,$am,$ad,$ay) < mktime(0,0,0,$bm,$bd,$by)) {

            return -1;

        } else {

            return 1;

        }

    }

}

?>



$d is the delimeter

jfren484 AT hotmail DOT com

13 years ago


If you've used ADO before, you may have used the Sort property on a recordset.  It's very powerful - you can add a nice ORDER BY clause after getting the recordset from the database.  It's especially helpful if you want to show a list on a web page and make the column headings links that cause the list to resort on that column.



I wanted to do the same thing with mysql recordsets, but it looks like you have to have the ORDER BY in your query.  I re-worked the example from johan_land at yahoo dot com above for sorting multidimensional arrays.  When I get a mysql recordset, I create an array with all of the records like this:



<?php

$aaRows[]    = array();

if (mysql_num_rows($rsRows) > 0)

    while ($aRow = mysql_fetch_array($rsRows, MYSQL_ASSOC))

        $aaRows[]    = $aRow;

?>



At this point $aaRows is an array of arrays - it's a numeric-indexed array containing records from the recordset, which themselves are associative arrays.  The following code takes the array of records as the first parameter, and an array of fields to sort - each field is an associative array, where 'name' is the db field name, and 'dir' is the direction to sort.  If dir is 'DESC' (case-insensitive), it will sort descending.  Any other value (including not setting one) will cause it to sort ascending.



<?php

function sortRows(&$a_aaRows, $a_aaSortCriteria)

{

    GLOBAL    $g_aaSortArray;



    function compare($a_aRow1, $a_aRow2, $a_lField = 0)

    {

        GLOBAL    $g_aaSortArray;



        $lCompareVal    = 0;



        if ($a_lField < count($g_aaSortArray))

        {

            $sSortFieldName    = $g_aaSortArray[$a_lField]['name'];

            $sSortFieldDir    = $g_aaSortArray[$a_lField]['dir'];



            $vValue1    = eval('return $a_aRow1[' . $sSortFieldName . '];');

            $vValue2    = eval('return $a_aRow2[' . $sSortFieldName . '];');



            if ($vValue1 == $vValue2)

                $lCompareVal    = compare($a_aRow1, $a_aRow2, $a_lField + 1);

            else

            {

                $lCompareVal    =    $vValue1 > $vValue2 ? 1 : -1;

                if (strtolower(substr($sSortFieldDir, 0, 4)) == 'desc')

                    $lCompareVal    = -$lCompareVal;

            }

        }



        return $lCompareVal;

    }



    $g_aaSortArray    = $a_aaSortCriteria;

    usort($a_aaRows, 'compare');

}

?>



When I call it it looks something like this:



<?php

sortRows($aaRows, array(array('name' => 'STATE', 'dir' => 'ASC'), array('name' => 'CITY', 'dir' => 'DESC')));

?>

graham at irwin dot org

14 years ago


Example 3 above does not work with 4.0.4pl1, unless you write the uasort line as follows:
uasort($a, array ($a[0], "cmp_obj"));

(I assume any instance of the object: a[0] or a[1] or a[2] would work as well)

It does not work at all with associative arrays of objects.

johan_land at yahoo dot com

14 years ago


These functions will sort an array by more than one element. The elements to sort by is specified in $sortArr. If you eg. want to sort by $destArr[]["sortBy2"][0] you add '["sortBy2"][0]' to $sortArr. Use it as much as you want!! If you modify it, please let me know...



<?php

//The functions

function compare($a, $b) {

    return cmpRec(0, $a, $b);

}



function cmpRec($i, $a, $b) {

    global $sortArr;

    if($i == sizeof($sortArr)) {

        return 0;

    }

    $avalue = '$avalue = $a'.$sortArr[$i].';';

    $bvalue = '$bvalue = $b'.$sortArr[$i].';';

    eval($avalue);

    eval($bvalue);

        if($avalue == $bvalue) {

        return cmpRec($i+1, $a, $b);

    } else {

        return ($avalue > $bvalue) ? (1) : (-1); 

    }

}



//For testing the functions

$destArr = array( array( "sortBy1" => 2, "sortBy2" => array( "Fish", "eat seafood" )), array( "sortBy1" => 1, "sortBy2" => array( "Lions", "eat everything" )), array( "sortBy1" => 1, "sortBy2" => array( "Bird", "eat birdfood" )) ); 

$sortArr = array( '["sortBy1"]', '["sortBy2"][0]' );

print_r($destArr);

usort($destArr, "compare");

reset($destArr);

print_r($destArr);

?>

todor at todor dot net

12 years ago


To sort multidimentional arrays .... by one key.



<?php

function multi_sort($tab,$key){

    $compare = create_function('$a,$b','if ($a["'.$key.'"] == $b["'.$key.'"]) {return 0;}else {return ($a["'.$key.'"] > $b["'.$key.'"]) ? -1 : 1;}');

    usort($tab,$compare) ;

    return $tab ;

}

?>

arjini at mac dot com

12 years ago


<?php
/*
This is a class I built to sort parent/child relationships of array elements.
I post this here, because thanks to usort, you can also assign an explicit order
to the elements.

I first built this to sort categories and subcategories.

My database has four fields. category_id, parent_id, category_name, category_position

$rows is an associative array from the database with my categories.
*/
$rows = array( 0=>array('category_id'=>1,'parent_id' =>3,'category_name' =>'Second Child','category_position'=>2),
                    1=>array('category_id' =>2,'parent_id' =>0,'category_name' =>'Second Parent','category_position'=>2),
                    2=>array('category_id' =>3,'parent_id' =>0,'category_name' =>'First Parent','category_position'=>1),
                    3=>array('category_id' =>4,'parent_id' =>0,'category_name' =>'Third Parent','category_position'=>3),
                    4=>array('category_id' =>5,'parent_id' =>3,'category_name' =>'First Child','category_position'=>1),
                    5=>array('category_id' =>6,'parent_id' =>5,'category_name'=>'Second Sub-Child','category_position'=>2),
                    6=>array('category_id' =>7,'parent_id' =>5,'category_name' =>'First Sub-Child','category_position'=>1)
                    );

$ordered = chain('category_id', 'parent_id', 'category_position', $rows);

foreach($ordered as $item)
{
    echo str_repeat('------', $item['indent']).$item['category_name'].'<br>';
}

/*

Output

First Parent
------First Child
------------First Sub-Child
------------Second Sub-Child
------Second Child
Second Parent
Third Parent

You can have it only return a certain "branch" if you specify a root_id.
Aditionally, you can keep it by going to deep by specifying max-level.

Hope someone finds this useful, I sure would have liked to see this here a week ago.

Ah yes... and the code that runs it.
*/

function chain($primary_field, $parent_field, $sort_field, $rows, $root_id=0, $maxlevel=25)
{
    $c = new chain($primary_field, $parent_field, $sort_field, $rows, $root_id, $maxlevel);
    return $c->chain_table;
}

class chain
{
    var $table;
    var $rows;
    var $chain_table;
    var $primary_field;
    var $parent_field;
    var $sort_field;
    
    function chain($primary_field, $parent_field, $sort_field, $rows, $root_id, $maxlevel)
    {
        $this->rows = $rows;
        $this->primary_field = $primary_field;
        $this->parent_field = $parent_field;
        $this->sort_field = $sort_field;
        $this->buildChain($root_id,$maxlevel);
    }

    function buildChain($rootcatid,$maxlevel)
    {
        foreach($this->rows as $row)
        {
            $this->table[$row[$this->parent_field]][ $row[$this->primary_field]] = $row;
        }
        $this->makeBranch($rootcatid,0,$maxlevel);
    }
            
    function makeBranch($parent_id,$level,$maxlevel)
    {
        $rows=$this->table[$parent_id];
        foreach($rows as $key=>$value)
        {
            $rows[$key]['key'] = $this->sort_field;
        }
        
        usort($rows,'chainCMP');
        foreach($rows as $item)
        {
            $item['indent'] = $level;
            $this->chain_table[] = $item;
            if((isset($this->table[$item[$this->primary_field]])) && (($maxlevel>$level+1) || ($maxlevel==0)))
            {
                $this->makeBranch($item[$this->primary_field], $level+1, $maxlevel);
            }
        }
    }
}

function chainCMP($a,$b)
{
    if($a[$a['key']] == $b[$b['key']])
    {
        return 0;
    }
    return($a[$a['key']]<$b[$b['key']])?-1:1;
}

?>

steveNO_SPAM at AXE_MEcontentwatch dot com

13 years ago


The sort functions do nothing if identical keys exist.  Of course, you shouldn't have identical keys anyway, but this just might save someone else the oodles of time it took me to figure out while using multi-dimentional arrays:



<?php

class myArticleList {

// ... //

  function &getList () {



    // works

        $a = array ( 

                   "articleList1" => array ( "2", "3" ),

                   "articleList2" => array ( "3" , "4")

                 );

    usort( $a, array( $this, "compareByTitle") );

      

    // doesn't work

        $b = array ( 

                   "articleList" => array ( "2", "3" ),

                   "articleList" => array ( "3" , "4")

                 );

    usort( $b, array( $this, "compareByTitle") );

  }



  function compareByTitle( $a, $b ) {

  // ... //

  }

}

?>

xnoguer at rezebra dot com

14 years ago


just for debugging purposes, usort does not complain if its argument function is not defined, i.e.:



<?php usort($my_array,"non existant function"); ?>



will not do anything...

bo at erichsen dot com

15 years ago


when using usort to refer to a function inside a class i have succesfully used:



<?php usort($myarray,array($this,"cmp")); ?>

Rogier

6 years ago


<?php
// I have seen many examples of sorting, almost all of which 
// are too specific and require one implementation per property
// on which to sort.
// So I decided to use Reflection, implementing a more generic approach that in fact turned out
// to resemble an approach I used in the early days of .NET...

// Intentionally, I did not do any checking on existing
// items. This is just to keep simplicity and to 
// demonstrate the sorting functionality.

// A more real-life appraoach would require e.g. a collection that is based
// on implementing the Iterator, ArrayAccess and Countable interfaces.

// Take note that this implementation is specific for PHP5+ only
// This code was tested on PHP 5.0.4

class SortableItem
{
    static public $sortProperty;
    
    static function USortAsc($a, $b)
    {
        /*@var $_pd ReflectionProperty*/
        $_pd = self::$sortProperty;
        if ($_pd !== null)
        {
            if ($_pd->getValue($a) === $_pd->getValue($b))
                return 0;
            else
                return (($_pd->getValue($a) < $_pd->getValue($b))?-1:1);
        }
        return 0;
    }

    static function USortDesc($a, $b)
    {
        return -(self::USortAsc($a,$b));
    }

}
class Item extends SortableItem
{
    public $name;
    public $index;
    public $description;
    
    function __construct($nam,$idx,$desc)
    {
        $this->name = $nam;
        $this->index = $idx;
        $this->description = $desc;
    }
    function __toString()
    {
        return "$this->index; $this->name; $this->description\n";
    }
}
class ItemCollection
{
    protected $_array = array();
    protected $_itemDescriptor;
    
    function __construct()
    {
        $this->_itemDescriptor = new ReflectionClass('Item');
    }
    
    function Add(Item $item)
    {
        $this->_array[] = $item;
    }
    
    function Sort($property, $asc=true)
    {
        // this is where sorting logic takes place
        $_pd = $this->_itemDescriptor->getProperty($property);
        if ($_pd == null)
        {
            user_error('Property '.$property.' does not exist in class '.$this->_itemDescriptor->getName(), E_WARNING);
            return;
        }
        // set sortDescriptor
        Item::$sortProperty = $_pd;
        // and apply sorting
        usort($this->_array, array('Item', ($asc?'USortAsc':'USortDesc')));
    }
    
    function getItems(){return $this->_array;}
}

//testing it....
$utime = microtime(true);
$coll = new ItemCollection();
$coll->Add( new Item('apple',0,'a sour fruit') );
$coll->Add( new Item('pear',54,'delicious pears') );
$coll->Add( new Item('mango',245,'bread and butter') );

echo PHP_EOL,'sort by index, asc',PHP_EOL;
$coll->Sort('index',true);
$items = $coll->getItems();
foreach($items as $item)
{
    echo $item->__toString();
}

echo PHP_EOL,'sort by index, desc',PHP_EOL;
$coll->Sort('index',false);
$items = $coll->getItems();
foreach($items as $item)
{
    echo $item->__toString();
}

echo PHP_EOL,'sort by name, asc',PHP_EOL;
$coll->Sort('name',true);
$items = $coll->getItems();
foreach($items as $item)
{
    echo $item->__toString();
}

echo PHP_EOL,'sort by name, desc',PHP_EOL;
$coll->Sort('name',false);
$items = $coll->getItems();
foreach($items as $item)
{
    echo $item->__toString();
}
$utime = microtime(true)-$utime;
echo PHP_EOL,' sorting all took ',round(1000*$utime,2),' ms';
?>

kristen at ccshoreline dot org

12 years ago


I have a class with a bunch of functions that work with an SQL database. I am working with calendar dates that occur more than once (like once a week for 2 months), so I have to generate the date in php after the SQL. But I wanted to sort the events based on the date, so I tried using usort, but was unable to get it to work, because it didn't think that my sorting function was defined (even though it was in the same class). I have a separate class to store the data, that has a variable called Start which is a PHP date object.



So here is how I got it to work. First I created a temporary function, that returned the value of a string comparison of the timestamps for the dates. Then I used that temporary function for the usort. Enjoy.



<?php

$tempfunction = create_function('$event1,$event2',

        'return strcmp($event1->Start[0],$event2->Start[0]);');

usort($data,$tempfunction);

?>

phpguy at lifetoward dot com

6 years ago


I recommend that you take special note of the fact that an INTEGER value must be returned from a sorting callback function. So, let's say you want to sort arrays by a quotient of two of their elements and to do so you write something like:
<?php
function sorter($a, $b) 
{ return $a['num']/$a['denom'] - $b['num']/$b['denom']; }
?>

You may not get the result you want because probably $x['num']/$x['denom'] has absolute value less than 1 and you'll get a lot of "same value" effective results from the comparator function as integer rounding occurs. 

To solve this just boost up the quotients to be big integers, then subtract them:

<?php
function sorter($a, $b) 
{ return 1000*$a['num']/$a['denom'] - 1000*$b['num']/$b['denom']; }
?>

usort

Description

Parameters

Return Values

Examples

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User Contributed Notes