(PHP 5 >= 5.5.0, PHP 7)
array_column — Return the values from a single column in the input array
array_column() returns the values from a single column of
the input, identified by the
column_key. Optionally, an
index_key may be provided to index the values in the
returned array by the values from the index_key
column of the input array.
inputA multi-dimensional array or an array of objects from which to pull a column of values from. If an array of objects is provided, then public properties can be directly pulled. In order for protected or private properties to be pulled, the class must implement both the __get() and __isset() magic methods.
column_key
The column of values to return. This value may be an integer key of the
column you wish to retrieve, or it may be a string key name for an
associative array or property name. It may also be NULL to return
complete arrays or objects (this is useful together with
index_key to reindex the array).
index_keyThe column to use as the index/keys for the returned array. This value may be the integer key of the column, or it may be the string key name.
Returns an array of values representing a single column from the input array.
| Version | Description |
|---|---|
| 7.0.0 |
Added the ability for the input parameter to be
an array of objects.
|
Example #1 Get the column of first names from a recordset
<?php
// Array representing a possible record set returned from a database
$records = array(
array(
'id' => 2135,
'first_name' => 'John',
'last_name' => 'Doe',
),
array(
'id' => 3245,
'first_name' => 'Sally',
'last_name' => 'Smith',
),
array(
'id' => 5342,
'first_name' => 'Jane',
'last_name' => 'Jones',
),
array(
'id' => 5623,
'first_name' => 'Peter',
'last_name' => 'Doe',
)
);
$first_names = array_column($records, 'first_name');
print_r($first_names);
?>
The above example will output:
Array
(
[0] => John
[1] => Sally
[2] => Jane
[3] => Peter
)
Example #2 Get the column of last names from a recordset, indexed by the "id" column
<?php
// Using the $records array from Example #1
$last_names = array_column($records, 'last_name', 'id');
print_r($last_names);
?>
The above example will output:
Array
(
[2135] => Doe
[3245] => Smith
[5342] => Jones
[5623] => Doe
)
Example #3 Get the column of usernames from the public "username" property of an object
<?php
class User
{
public $username;
public function __construct(string $username)
{
$this->username = $username;
}
}
$users = [
new User('user 1'),
new User('user 2'),
new User('user 3'),
];
print_r(array_column($users, 'username'));
?>
The above example will output:
Array
(
[0] => user 1
[1] => user 2
[2] => user 3
)
Example #4 Get the column of names from the private "name" property of an object using the magic __get() method.
<?php
class Person
{
private $name;
public function __construct(string $name)
{
$this->name = $name;
}
public function __get($prop)
{
return $this->$prop;
}
public function __isset($prop) : bool
{
return isset($this->$prop);
}
}
$people = [
new Person('Fred'),
new Person('Jane'),
new Person('John'),
];
print_r(array_column($people, 'name'));
?>
The above example will output:
Array
(
[0] => Fred
[1] => Jane
[2] => John
)
if array_column does not exist the below solution will work.
if(!function_exists("array_column"))
{
function array_column($array,$column_name)
{
return array_map(function($element) use($column_name){return $element[$column_name];}, $array);
}
}
I added a little more functionality to the more popular answers here to support the $index_key parameter for PHP < 5.5
<?php
// for php < 5.5
if (!function_exists('array_column')) {
function array_column($input, $column_key, $index_key = null) {
$arr = array_map(function($d) use ($column_key, $index_key) {
if (!isset($d[$column_key])) {
return null;
}
if ($index_key !== null) {
return array($d[$index_key] => $d[$column_key]);
}
return $d[$column_key];
}, $input);
if ($index_key !== null) {
$tmp = array();
foreach ($arr as $ar) {
$tmp[key($ar)] = current($ar);
}
$arr = $tmp;
}
return $arr;
}
}
?>
You can also use array_map fucntion if you haven't array_column().
example:
$a = array(
array(
'id' => 2135,
'first_name' => 'John',
'last_name' => 'Doe',
),
array(
'id' => 3245,
'first_name' => 'Sally',
'last_name' => 'Smith',
)
);
array_column($a, 'last_name');
becomes
array_map(function($element){return $element['last_name'];}, $a);
Some remarks not included in the official documentation.
1) array_column does not support 1D arrays, in which case an empty array is returned.
2) The $column_key is zero-based.
3) If $column_key extends the valid index range an empty array is returned.
if (!function_exists('array_column'))
{
function array_column($input, $column_key=null, $index_key=null)
{
$result = array();
$i = 0;
foreach ($input as $v)
{
$k = $index_key === null || !isset($v[$index_key]) ? $i++ : $v[$index_key];
$result[$k] = $column_key === null ? $v : (isset($v[$column_key]) ? $v[$column_key] : null);
}
return $result;
}
}
My version is closer to the original than http://github.com/ramsey/array_column
<?php
/**
* Provides functionality for array_column() to projects using PHP earlier than
* version 5.5.
* @copyright (c) 2015 WinterSilence (http://github.com/WinterSilence)
* @license MIT
*/
if (!function_exists('array_column')) {
/**
* Returns an array of values representing a single column from the input
* array.
* @param array $array A multi-dimensional array from which to pull a
* column of values.
* @param mixed $columnKey The column of values to return. This value may
* be the integer key of the column you wish to retrieve, or it may be
* the string key name for an associative array. It may also be NULL to
* return complete arrays (useful together with index_key to reindex
* the array).
* @param mixed $indexKey The column to use as the index/keys for the
* returned array. This value may be the integer key of the column, or
* it may be the string key name.
* @return array
*/
function array_column(array $array, $columnKey, $indexKey = null)
{
$result = array();
foreach ($array as $subArray) {
if (!is_array($subArray)) {
continue;
} elseif (is_null($indexKey) && array_key_exists($columnKey, $subArray)) {
$result[] = $subArray[$columnKey];
} elseif (array_key_exists($indexKey, $subArray)) {
if (is_null($columnKey)) {
$result[$subArray[$indexKey]] = $subArray;
} elseif (array_key_exists($columnKey, $subArray)) {
$result[$subArray[$indexKey]] = $subArray[$columnKey];
}
}
}
return $result;
}
}
?>
Note that this function will return the last entry when possible keys are duplicated.
<?php
$array = array(
array(
'1-1',
'one',
'one',
),
array(
'1-2',
'two',
'one',
),
);
var_dump(array_column($array, $value = 0, $index = 1));
var_dump(array_column($array, $value = 0, $index = 2));
// returns:
/*
array (size=2)
'one' => string '1-1' (length=3)
'two' => string '1-2' (length=3)
array (size=1)
'one' => string '1-2' (length=3)
*/
?>
If you need to extract more than one column from an array, you can use array_intersect_key on each element, like so:
function array_column_multi(array $input, array $column_keys) {
$result = array();
$column_keys = array_flip($column_keys);
foreach($input as $key => $el) {
$result[$key] = array_intersect_key($el, $column_keys);
}
return $result;
}
Please note this function accepts 2D-arrays ONLY, and silently returns empty array when non-array argument is provided.
Code:
class testObject {
public $a = 123;
}
$testArray = [new testObject(), new testObject(), new testObject()];
$result = array_column($testArray, 'a')); //array(0) { }
a simple solution:
function arrayColumn(array $array, $column_key, $index_key=null){
if(function_exists('array_column ')){
return array_column($array, $column_key, $index_key);
}
$result = [];
foreach($array as $arr){
if(!is_array($arr)) continue;
if(is_null($column_key)){
$value = $arr;
}else{
$value = $arr[$column_key];
}
if(!is_null($index_key)){
$key = $arr[$index_key];
$result[$key] = $value;
}else{
$result[] = $value;
}
}
return $result;
}
If array_column is not available you can use the following function, which also has the $index_key parameter:
if (!function_exists('array_column')) {
function array_column($array, $column_key, $index_key = null)
{
return array_reduce($array, function ($result, $item) use ($column_key, $index_key)
{
if (null === $index_key) {
$result[] = $item[$column_key];
} else {
$result[$item[$index_key]] = $item[$column_key];
}
return $result;
}, []);
}
}
Value for existing key in the resulting array is rewritten with new value if it exists in another source sub-array.
Another option for older PHP versions (pre 5.5.0) is to use array_walk():
<?php
$array = array(
array('some' => 'var', 'foo' => 'bar'),
array('some' => 'var', 'foo' => 'bar'),
array('some' => 'var', 'foo' => 'bar')
);
array_walk($array, function(&$value, $key, $return) {
$value = $value[$return];
}, 'foo');
print_r($array);
// Array
// (
// [0] => bar
// [1] => bar
// [2] => bar
// )
?>
This didn't work for me recursively and needed to come up with a solution.
Here's my solution to the function:
if ( ! function_exists( 'array_column_recursive' ) ) {
/**
* Returns the values recursively from columns of the input array, identified by
* the $columnKey.
*
* Optionally, you may provide an $indexKey to index the values in the returned
* array by the values from the $indexKey column in the input array.
*
* @param array $input A multi-dimensional array (record set) from which to pull
* a column of values.
* @param mixed $columnKey The column of values to return. This value may be the
* integer key of the column you wish to retrieve, or it
* may be the string key name for an associative array.
* @param mixed $indexKey (Optional.) The column to use as the index/keys for
* the returned array. This value may be the integer key
* of the column, or it may be the string key name.
*
* @return array
*/
function array_column_recursive( $input = NULL, $columnKey = NULL, $indexKey = NULL ) {
// Using func_get_args() in order to check for proper number of
// parameters and trigger errors exactly as the built-in array_column()
// does in PHP 5.5.
$argc = func_num_args();
$params = func_get_args();
if ( $argc < 2 ) {
trigger_error( "array_column_recursive() expects at least 2 parameters, {$argc} given", E_USER_WARNING );
return NULL;
}
if ( ! is_array( $params[ 0 ] ) ) {
// Because we call back to this function, check if call was made by self to
// prevent debug/error output for recursiveness :)
$callers = debug_backtrace();
if ( $callers[ 1 ][ 'function' ] != 'array_column_recursive' ){
trigger_error( 'array_column_recursive() expects parameter 1 to be array, ' . gettype( $params[ 0 ] ) . ' given', E_USER_WARNING );
}
return NULL;
}
if ( ! is_int( $params[ 1 ] )
&& ! is_float( $params[ 1 ] )
&& ! is_string( $params[ 1 ] )
&& $params[ 1 ] !== NULL
&& ! ( is_object( $params[ 1 ] ) && method_exists( $params[ 1 ], '__toString' ) )
) {
trigger_error( 'array_column_recursive(): The column key should be either a string or an integer', E_USER_WARNING );
return FALSE;
}
if ( isset( $params[ 2 ] )
&& ! is_int( $params[ 2 ] )
&& ! is_float( $params[ 2 ] )
&& ! is_string( $params[ 2 ] )
&& ! ( is_object( $params[ 2 ] ) && method_exists( $params[ 2 ], '__toString' ) )
) {
trigger_error( 'array_column_recursive(): The index key should be either a string or an integer', E_USER_WARNING );
return FALSE;
}
$paramsInput = $params[ 0 ];
$paramsColumnKey = ( $params[ 1 ] !== NULL ) ? (string) $params[ 1 ] : NULL;
$paramsIndexKey = NULL;
if ( isset( $params[ 2 ] ) ) {
if ( is_float( $params[ 2 ] ) || is_int( $params[ 2 ] ) ) {
$paramsIndexKey = (int) $params[ 2 ];
} else {
$paramsIndexKey = (string) $params[ 2 ];
}
}
$resultArray = array();
foreach ( $paramsInput as $row ) {
$key = $value = NULL;
$keySet = $valueSet = FALSE;
if ( $paramsIndexKey !== NULL && array_key_exists( $paramsIndexKey, $row ) ) {
$keySet = TRUE;
$key = (string) $row[ $paramsIndexKey ];
}
if ( $paramsColumnKey === NULL ) {
$valueSet = TRUE;
$value = $row;
} elseif ( is_array( $row ) && array_key_exists( $paramsColumnKey, $row ) ) {
$valueSet = TRUE;
$value = $row[ $paramsColumnKey ];
}
$possibleValue = array_column_recursive( $row, $paramsColumnKey, $paramsIndexKey );
if ( $possibleValue ) {
$resultArray = array_merge( $possibleValue, $resultArray );
}
if ( $valueSet ) {
if ( $keySet ) {
$resultArray[ $key ] = $value;
} else {
$resultArray[ ] = $value;
}
}
}
return $resultArray;
}
}
