strpos

(PHP 4, PHP 5, PHP 7)

strpos — Find the position of the first occurrence of a substring in a string

Description

mixed strpos ( string $haystack , mixed $needle [, int $offset = 0 ] )

Find the numeric position of the first occurrence of needle in the haystack string.

Parameters

haystack: The string to search in.
needle: If needle is not a string, it is converted to an integer and applied as the ordinal value of a character.
offset: If specified, search will start this number of characters counted from the beginning of the string. Unlike strrpos() and strripos(), the offset cannot be negative.

Return Values

Returns the position of where the needle exists relative to the beginning of the haystack string (independent of offset). Also note that string positions start at 0, and not 1.

Returns FALSE if the needle was not found.

Warning

This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE. Please read the section on Booleans for more information. Use the === operator for testing the return value of this function.

Examples

Example #1 Using ===


<?php
$mystring = 'abc';
$findme   = 'a';
$pos = strpos($mystring, $findme);

// Note our use of ===.  Simply == would not work as expected
// because the position of 'a' was the 0th (first) character.
if ($pos === false) {
    echo "The string '$findme' was not found in the string '$mystring'";
} else {
    echo "The string '$findme' was found in the string '$mystring'";
    echo " and exists at position $pos";
}
?>

Example #2 Using !==


<?php
$mystring = 'abc';
$findme   = 'a';
$pos = strpos($mystring, $findme);

// The !== operator can also be used.  Using != would not work as expected
// because the position of 'a' is 0. The statement (0 != false) evaluates 
// to false.
if ($pos !== false) {
     echo "The string '$findme' was found in the string '$mystring'";
         echo " and exists at position $pos";
} else {
     echo "The string '$findme' was not found in the string '$mystring'";
}
?>

Example #3 Using an offset


<?php
// We can search for the character, ignoring anything before the offset
$newstring = 'abcdef abcdef';
$pos = strpos($newstring, 'a', 1); // $pos = 7, not 0
?>

Notes

Note: This function is binary-safe.

User Contributed Notes

8 years ago


WARNING

As strpos may return either FALSE (substring absent) or 0 (substring at start of string), strict versus loose equivalency operators must be used very carefully.

To know that a substring is absent, you must use:  

=== FALSE

To know that a substring is present (in any position including 0), you can use either of:

!== FALSE  (recommended)
 > -1  (note: or greater than any negative number)

To know that a substring is at the start of the string, you must use:  

=== 0

To know that a substring is in any position other than the start, you can use any of: 

 > 0  (recommended)
!= 0  (note: but not !== 0 which also equates to FALSE)
!= FALSE  (disrecommended as highly confusing)

Also note that you cannot compare a value of "" to the returned value of strpos. With a loose equivalence operator (== or !=) it will return results which don't distinguish between the substring's presence versus position. With a strict equivalence operator (=== or !==) it will always return false.

mtroy dot student at gmail dot com

4 years ago


when you want to know how much of substring occurrences, you'll use "substr_count".
But, retrieve their positions, will be harder.
So, you can do it by starting with the last occurrence :

function strpos_r($haystack, $needle)
{
    if(strlen($needle) > strlen($haystack))
        trigger_error(sprintf("%s: length of argument 2 must be <= argument 1", __FUNCTION__), E_USER_WARNING);

    $seeks = array();
    while($seek = strrpos($haystack, $needle))
    {
        array_push($seeks, $seek);
        $haystack = substr($haystack, 0, $seek);
    }
    return $seeks;
}

it will return an array of all occurrences a the substring in the string

Example : 

$test = "this is a test for testing a test function... blah blah";
var_dump(strpos_r($test, "test"));

// output 

array(3) {
  [0]=>
  int(29)
  [1]=>
  int(19)
  [2]=>
  int(10)
}

Paul-antoine
Malézieux.

rjeggens at ijskoud dot org

4 years ago


I lost an hour before I noticed that strpos only returns FALSE as a boolean, never TRUE.. This means that

strpos() !== false 

is a different beast then:

strpos() === true

since the latter will never be true. After I found out, The warning in the documentation made a lot more sense.

akarmenia at gmail dot com

5 years ago


My version of strpos with needles as an array. Also allows for a string, or an array inside an array.

<?php
function strpos_array($haystack, $needles) {
    if ( is_array($needles) ) {
        foreach ($needles as $str) {
            if ( is_array($str) ) {
                $pos = strpos_array($haystack, $str);
            } else {
                $pos = strpos($haystack, $str);
            }
            if ($pos !== FALSE) {
                return $pos;
            }
        }
    } else {
        return strpos($haystack, $needles);
    }
}

// Test
echo strpos_array('This is a test', array('test', 'drive')); // Output is 10

?>

ohcc at 163 dot com

1 year ago


Be careful when the $haystack or $needle parameter is an integer.
If you are not sure of its type, you should  convert it into a string.
<?php
    var_dump(strpos(12345,1));//false
    var_dump(strpos(12345,'1'));//0
    var_dump(strpos('12345',1));//false
    var_dump(strpos('12345','1'));//0
    $a = 12345;
    $b = 1;
    var_dump(strpos(strval($a),strval($b)));//0
    var_dump(strpos((string)$a,(string)$b));//0    
?>

teddanzig at yahoo dot com

7 years ago


routine to return -1 if there is no match for strpos



<?php

//instr function to mimic vb instr fucntion

function InStr($haystack, $needle)

{

    $pos=strpos($haystack, $needle);

    if ($pos !== false)

    {

        return $pos;

    }

    else

    {

        return -1;

    }

}

?>

Achintya

6 years ago


A function I made to find the first occurrence of a particular needle not enclosed in quotes(single or double). Works for simple nesting (no backslashed nesting allowed).



<?php

function strposq($haystack, $needle, $offset = 0){

    $len = strlen($haystack);

    $charlen = strlen($needle);

    $flag1 = false;

    $flag2 = false;

    for($i = $offset; $i < $len; $i++){

        if(substr($haystack, $i, 1) == "'"){

            $flag1 = !$flag1 && !$flag2 ? true : false;

        }

        if(substr($haystack, $i, 1) == '"'){

            $flag2 = !$flag1 && !$flag2 ? true : false;

        }

        if(substr($haystack, $i, $charlen) == $needle && !$flag1 && !$flag2){

            return $i;        

        }

    }

    return false;

}



echo strposq("he'llo'character;\"'som\"e;crap", ";"); //16

?>

qrworld.net

1 year ago


I found a function in this post http://softontherocks.blogspot.com/2014/11/buscar-multiples-textos-en-un-texto-con.html 
that implements the search in both ways, case sensitive or case insensitive, depending on an input parameter.

The function is:

function getMultiPos($haystack, $needles, $sensitive=true, $offset=0){
    foreach($needles as $needle) {
        $result[$needle] = ($sensitive) ? strpos($haystack, $needle, $offset) : stripos($haystack, $needle, $offset);
    }
    return $result;
}

It was very useful for me.

ilaymyhat-rem0ve at yahoo dot com

8 years ago


This might be useful.



<?php

class String{

    

    //Look for a $needle in $haystack in any position

    public static function contains(&$haystack, &$needle, &$offset)

    {

        $result = strpos($haystack, $needle, $offset);

        return $result !== FALSE;

    }

    

    //intuitive implementation .. if not found returns -1.

    public static function strpos(&$haystack, &$needle, &$offset)

    {

        $result = strpos($haystack, $needle, $offset);

        if ($result === FALSE )

        {

            return -1;

        }

        return $result;

    }

    

}//String

?>

spinicrus at gmail dot com

9 years ago


if you want to get the position of a substring relative to a substring of your string, BUT in REVERSE way:

<?php

function strpos_reverse_way($string,$charToFind,$relativeChar) {
    //
    $relativePos = strpos($string,$relativeChar);
    $searchPos = $relativePos;
    $searchChar = '';
    //
    while ($searchChar != $charToFind) {
        $newPos = $searchPos-1;
        $searchChar = substr($string,$newPos,strlen($charToFind));
        $searchPos = $newPos;
    }
    //
    if (!empty($searchChar)) {
        //
        return $searchPos;
        return TRUE;
    }
    else {
        return FALSE;
    }
    //
}

?>

usulaco at gmail dot com

5 years ago


Parse strings between two others in to array.



<?php

function g($string,$start,$end){

     preg_match_all('/' . preg_quote($start, '/') . '(.*?)'. preg_quote($end, '/').'/i', $string, $m);

     $out = array();



     foreach($m[1] as $key => $value){

       $type = explode('::',$value);

       if(sizeof($type)>1){

          if(!is_array($out[$type[0]]))

             $out[$type[0]] = array();

          $out[$type[0]][] = $type[1];

       } else {

          $out[] = $value;

       }

     }

  return $out;

}

print_r(g('Sample text, [/text to extract/] Rest of sample text [/WEB::http://google.com/] bla bla bla. ','[/','/]'));

?>



results:

Array

(

    [0] => text to extract

    [WEB] => Array

        (

            [0] => http://google.com

        )



)



Can be helpfull to custom parsing :)

bishop

12 years ago


Code like this:
<?php
if (strpos('this is a test', 'is') !== false) {
    echo "found it";
}
?>

gets repetitive, is not very self-explanatory, and most people handle it incorrectly anyway. Make your life easier:

<?php
function str_contains($haystack, $needle, $ignoreCase = false) {
    if ($ignoreCase) {
        $haystack = strtolower($haystack);
        $needle   = strtolower($needle);
    }
    $needlePos = strpos($haystack, $needle);
    return ($needlePos === false ? false : ($needlePos+1));
}
?>

Then, you may do:
<?php
// simplest use
if (str_contains('this is a test', 'is')) {
    echo "Found it";
}

// when you need the position, as well whether it's present
$needlePos = str_contains('this is a test', 'is');
if ($needlePos) {
    echo 'Found it at position ' . ($needlePos-1);
}

// you may also ignore case
$needlePos = str_contains('this is a test', 'IS', true);
if ($needlePos) {
    echo 'Found it at position ' . ($needlePos-1);
}
?>

olmstead31 at yahoo dot com

6 years ago


I found that whatever I was using as a test with strpos it came out false exept if $pos was == 1

I figured it gives me a numeric value if found else it is null or false
here is what i did to make my code work:

<?php
//EXAMPLE 1:
$quiamime = ',64,68,70,';
$me = '64'
$posi = strpos($quiaime, ",$me,");  //posi is equal to 0
if (!is_numeric($posi)){
 //code here
}else{
  //else code here
}

//EXAMPLE 2:
$quiamime = ',68,70,64,';
$me = '64'
$posi = strpos($quiaime, ",$me,");  //posi is equal to 6
if (!is_numeric($posi)){
 //code here
}else{
  //else code here
}

//EXAMPLE 3:
$quiamime = ',68,70,';
$me = '64'
$posi = strpos($quiaime, ",$me,");  //posi is equal to NULL or FALSE
if (!is_numeric($posi)){
 //code here
}else{
  //else code here
}
?>

Anonymous

3 years ago


The most straightforward way to prevent this function from returning 0 is:

  strpos('x'.$haystack, $needle, 1)

The 'x' is simply a garbage character which is only there to move everything 1 position.
The number 1 is there to make sure that this 'x' is ignored in the search.
This way, if $haystack starts with $needle, then the function returns 1 (rather than 0).

digitalpbk [at] gmail.com

6 years ago


This function raises a warning if the offset is not between 0 and the length of string:



Warning: strpos(): Offset not contained in string in %s on line %d

Anonymous

1 month ago


## html 
# HEading 

&nbsp
Click here to go to the support pages.
Click here to submit a bug report.
Click here to request a feature.
(Again, please note, if you ask a question, report a bug, or request a feature, your note will be deleted.)

***heading***

fabio at naoimporta dot com

2 months ago


It is interesting to be aware of the behavior when the treatment of strings with characters using different encodings.

<?php
# Works like expected. There is no accent
var_dump(strpos("Fabio", 'b'));
#int(2)

# The "á" letter is occupying two positions
var_dump(strpos("Fábio", 'b')) ;
#int(3)

# Now, encoding the string "Fábio" to utf8, we get some "unexpected" outputs. Every letter that is no in regular ASCII table, will use 4 positions(bytes). The starting point remains like before.
# We cant find the characted, because the haystack string is now encoded.
var_dump(strpos(utf8_encode("Fábio"), 'á'));
#bool(false)

# To get the expected result, we need to encode the needle too
var_dump(strpos(utf8_encode("Fábio"), utf8_encode('á')));
#int(1) 

# And, like said before, "á" occupies 4 positions(bytes)
var_dump(strpos(utf8_encode("Fábio"), 'b'));
#int(5)

Andres

1 year ago


strpos: Want to find lines in text file, NOT beginning with a comment (// for example)?
That way it Works:
$komm=strpos($var,'//');
if($komm === FALSE || $komm == TRUE){}

Generally, it is a nonsense. Why 'strpos' cant ALWAYS output an integer?

binodluitel at hotmail dot com

2 years ago


This function will return 0 if the string that you are searching matches i.e. needle matches the haystack

{code}
echo strpos('bla', 'bla');
{code}

Output: 0

martijn at martijnfrazer dot nl

4 years ago


This is a function I wrote to find all occurrences of a string, using strpos recursively.

<?php
function strpos_recursive($haystack, $needle, $offset = 0, &$results = array()) {                
    $offset = strpos($haystack, $needle, $offset);
    if($offset === false) {
        return $results;            
    } else {
        $results[] = $offset;
        return strpos_recursive($haystack, $needle, ($offset + 1), $results);
    }
}
?>

This is how you use it:

<?php
$string = 'This is some string';
$search = 'a';
$found = strpos_recursive($string, $search);

if($found) {
    foreach($found as $pos) {
        echo 'Found "'.$search.'" in string "'.$string.'" at position <b>'.$pos.'</b><br />';
    }    
} else {
    echo '"'.$search.'" not found in "'.$string.'"';
}
?>

harshitpatelrock25 at gmail dot com

2 years ago


TO find the position specific word in a para:-

<?php
  $String = 'This is the php language And is Used to develop web programs';
  $find = '1232';
  $find_leg = strlen($find);
  $start_pos = 00;
  
  while($string_pos = strpos($String,$find,$start_pos)){
      echo "<strong> \" $find \" </strong> was found on position : $string_pos <br>" ;
     $start_pos = $string_pos + $find_leg;
  }
?>

gjh42 - simonokewode at hotmail dot com

4 years ago


A pair of functions to replace every nth occurrence of a string with another string, starting at any position in the haystack. The first works on a string and the second works on a single-level array of strings, treating it as a single string for replacement purposes (any needles split over two array elements are ignored).

Can be used for formatting dynamically-generated HTML output without touching the original generator: e.g. add a newLine class tag to every third item in a floated list, starting with the fourth item.
 
<?php
/* String Replace at Intervals   by Glenn Herbert (gjh42)    2010-12-17
 */
 
//(basic locator by someone else - name unknown)
//strnposr() - Find the position of nth needle in haystack.
function strnposr($haystack, $needle, $occurrence, $pos = 0) {
    return ($occurrence<2)?strpos($haystack, $needle, $pos):strnposr($haystack,$needle,$occurrence-1,strpos($haystack, $needle, $pos) + 1);
}

//gjh42
//replace every nth occurrence of $needle with $repl, starting from any position
function str_replace_int($needle, $repl, $haystack, $interval, $first=1, $pos=0) {
  if ($pos >= strlen($haystack) or substr_count($haystack, $needle, $pos) < $first) return $haystack;
  $firstpos = strnposr($haystack, $needle, $first, $pos);
  $nl = strlen($needle);
  $qty = floor(substr_count($haystack, $needle, $firstpos + 1)/$interval);
  do { //in reverse order
    $nextpos = strnposr($haystack, $needle, ($qty * $interval) + 1, $firstpos); 
    $qty--;
    $haystack = substr_replace($haystack, $repl, $nextpos, $nl);
  } while ($nextpos > $firstpos);
  return $haystack;
}
  //$needle = string to find
  //$repl = string to replace needle
  //$haystack = string to do replacing in
  //$interval = number of needles in loop
  //$first=1 = first occurrence of needle to replace (defaults to first) 
  //$pos=0 = position in haystack string to start from (defaults to first) 
 
//replace every nth occurrence of $needle with $repl, starting from any position, in a single-level array
function arr_replace_int($needle, $repl, $arr, $interval, $first=1, $pos=0, $glue='|+|') {
  if (!is_array($arr))  return $arr;
  foreach($arr as $key=>$value){
    if (is_array($arr[$key])) return $arr;
  }
  $haystack = implode($glue, $arr);
  $haystack = str_replace_int($needle, $repl, $haystack, $interval, $first, $pos);
  $tarr = explode($glue, $haystack);
  $i = 0;
  foreach($arr as $key=>$value){
    $arr[$key] = $tarr[$i];
    $i++;
  }
  return $arr;
}
?>
If $arr is not an array, or a multilevel array, it is returned unchanged.

jim at terrys dot net

4 years ago


strpos that accepts an array for $needle



<?php

// strpos that takes an array of values to match against a string

// note the stupid argument order (to match strpos)

function strpos_arr($haystack, $needle) {

    if(!is_array($needle)) $needle = array($needle);

    foreach($needle as $what) {

        if(($pos = strpos($haystack, $what))!==false) return $pos;

    }

    return false;

}

?>

gambajaja at yahoo dot com

5 years ago


<?php
$my_array = array ('100,101', '200,201', '300,301');
$check_me_in = array ('100','200','300','400');
foreach ($check_me_in as $value_cmi){
    $is_in=FALSE; #asume that $check_me_in isn't in $my_array
    foreach ($my_array as $value_my){
        $pos = strpos($value_my, $value_cmi);
        if ($pos===0)
            $pos++;
        if ($pos==TRUE){
            $is_in=TRUE;
            $value_my2=$value_my;
            }
    }
    if ($is_in) echo "ID $value_cmi in \$check_me_in I found in value '$value_my2' \n";
}
?>

The above example will output
ID 100 in $check_me_in I found in value '100,101' 
ID 200 in $check_me_in I found in value '200,201' 
ID 300 in $check_me_in I found in value '300,301'

yasindagli at gmail dot com

6 years ago


This function finds postion of nth occurence of a letter starting from offset.

<?php
function nth_position($str, $letter, $n, $offset = 0){
    $str_arr = str_split($str);
    $letter_size = array_count_values(str_split(substr($str, $offset)));
    if( !isset($letter_size[$letter])){
        trigger_error('letter "' . $letter . '" does not exist in ' . $str . ' after ' . $offset . '. position', E_USER_WARNING);
        return false;
    } else if($letter_size[$letter] < $n) {
        trigger_error('letter "' . $letter . '" does not exist ' . $n .' times in ' . $str . ' after ' . $offset . '. position', E_USER_WARNING);
        return false;
    }
    for($i = $offset, $x = 0, $count = (count($str_arr) - $offset); $i < $count, $x != $n; $i++){
        if($str_arr[$i] == $letter){
            $x++;
        }
    }
    return $i - 1;
}

echo nth_position('foobarbaz', 'a', 2); //7
echo nth_position('foobarbaz', 'b', 1, 4); //6
?>

ah dot d at hotmail dot com

6 years ago


A strpos modification to return an array of all the positions of a needle in the haystack 



<?php

function strallpos($haystack,$needle,$offset = 0){

    $result = array();

    for($i = $offset; $i<strlen($haystack); $i++){

        $pos = strpos($haystack,$needle,$i);

        if($pos !== FALSE){

            $offset =  $pos;

            if($offset >= $i){

                $i = $offset;

                $result[] = $offset;

            }

        }

    }

    return $result;

}

?>



example:-



<?php

$haystack = "ASD is trying to get out of the ASDs cube but the other ASDs told him that his behavior will destroy the ASDs world";



$needle = "ASD";



print_r(strallpos($haystack,$needle));



//getting all the positions starting from a specified position



print_r(strallpos($haystack,$needle,34));

?>

Tim

7 years ago


If you would like to find all occurences of a needle inside a haystack you could use this function strposall($haystack,$needle);. It will return an array with all the strpos's.



<?php

/**

 * strposall

 * 

 * Find all occurrences of a needle in a haystack

 *

 * @param string $haystack

 * @param string $needle

 * @return array or false

 */

function strposall($haystack,$needle){

    

    $s=0;

    $i=0;

    

    while (is_integer($i)){

        

        $i = strpos($haystack,$needle,$s);

        

        if (is_integer($i)) { 

            $aStrPos[] = $i; 

            $s = $i+strlen($needle); 

        }

    }

    if (isset($aStrPos)) { 

        return $aStrPos; 

    } 

    else { 

        return false; 

    }

}

?>

user at nomail dot com

8 years ago


This is a bit more useful when scanning a large string for all occurances between 'tags'.

<?php
function getStrsBetween($s,$s1,$s2=false,$offset=0) {
    /*====================================================================
    Function to scan a string for items encapsulated within a pair of tags

    getStrsBetween(string, tag1, <tag2>, <offset>

    If no second tag is specified, then match between identical tags

    Returns an array indexed with the encapsulated text, which is in turn
    a sub-array, containing the position of each item.

    Notes:
    strpos($needle,$haystack,$offset)
    substr($string,$start,$length)

    ====================================================================*/

    if( $s2 === false ) { $s2 = $s1; }
    $result = array();
    $L1 = strlen($s1);
    $L2 = strlen($s2);

    if( $L1==0 || $L2==0 ) {
        return false;
    }

    do {
        $pos1 = strpos($s,$s1,$offset);

        if( $pos1 !== false ) {
            $pos1 += $L1;

            $pos2 = strpos($s,$s2,$pos1);

            if( $pos2 !== false ) {
                $key_len = $pos2 - $pos1;

                $this_key = substr($s,$pos1,$key_len);

                if( !array_key_exists($this_key,$result) ) {
                    $result[$this_key] = array();
                }

                $result[$this_key][] = $pos1;

                $offset = $pos2 + $L2;
            } else {
                $pos1 = false;
            }
        }
    } while($pos1 !== false );

    return $result;
}
?>

dale at ucsc dot edu

10 years ago


if you want need a fast function to find the first occurrence of any ch element of an needle array this function might be of use: 
<?php
$eurl = strpos_needle_array($text, array('"'=>0,'\''=>0,'>'=>0, ' '=>0, "\n"=>0), $surl);

function strpos_needle_array(& $text, $needle_ary, $offset=0){    
    for($ch_pos=$offset;$ch_pos<strlen($text);$ch_pos++){
        if(isset($needle_ary[$text[$ch_pos]])){
            return $ch_pos;
        }
    }
    return false;
}
?>

arias at elleondeoro dot com

11 years ago


If you want to get all positions in an array, you can use this function. If the optional parameter count is especified, the function will put there the number of matches.



<?php

function strallpos($pajar, $aguja, $offset=0, &$count=null) {

  if ($offset > strlen($pajar)) trigger_error("strallpos(): Offset not contained in string.", E_USER_WARNING);

  $match = array();

  for ($count=0; (($pos = strpos($pajar, $aguja, $offset)) !== false); $count++) {

    $match[] = $pos;

    $offset = $pos + strlen($aguja);

  }

  return $match;

}

?>

philip

11 years ago


Many people look for in_string which does not exist in PHP, so, here's the most efficient form of in_string() (that works in both PHP 4/5) that I can think of:

<?php

function in_string($needle, $haystack, $insensitive = false) {

    if ($insensitive) {

        return false !== stristr($haystack, $needle);

    } else {

        return false !== strpos($haystack, $needle);

    }

}

?>

jburns131 at jbwebware dot com

7 years ago


The Situation:

I wanted to return TRUE if strpos returned position 0, and only position 0, without the added overhead of preg_match.

The Solution:

As PHP treats 0 (zero) as NULL, and strpos returns the int 0 (but not NULL), I used type casting and the "===" comparison operator (as it compares types) to resolve my issue.

<?php

$hayStack = "dbHost";
$needle  = "db"
$needlePos = strpos($hayStack, $needle);

if((string)$needlePos === (string)0) {
    echo "db is in position zero";
} else {
    echo "db is NOT in position zero";
}

?>

Returns:
db is in position zero

<?php

$hayStack = "another_db_host";
$needle  = "db"
$needlePos = strpos($hayStack, $needle);

if((string)$needlePos === (string)0) {
    echo "db is in position zero";
} else {
    echo "db is NOT in position zero";
}

?>

This returns:
db is in NOT position zero

gal_chen123 at hotmail dot co dot il

9 years ago


this function returns the text between 2 strings:



<?php

function get_between ($text, $s1, $s2) {

    $mid_url = "";

    $pos_s = strpos($text,$s1);

    $pos_e = strpos($text,$s2);

    for ( $i=$pos_s+strlen($s1) ; ( ( $i < ($pos_e)) && $i < strlen($text) ) ; $i++ ) {

        $mid_url .= $text[$i];

    }

    return $mid_url;

}

?>



if $s1 or $s2 are not found, $mid_url will be empty

to add an offset, simply compare $pos_s to the offset, and only let it continue if the offset is smaller then $pos_s.

mickRacky

7 years ago


here's a php implementation of stdc++ string class find_first_of using strpos.



<?php

function find_first_of($haystack, $needlesAsString, $offset=0)

{

  $max = strlen($needlesAsString);

  $index = strlen($haystack)+1;

  for($ii=0; $ii<$max;$ii++){

    $result = strpos($haystack,$needlesAsString[$ii], $offset);

    if( $result !== FALSE  && $result < $index)

      $index = $result;

  }

  return ( $index > strlen($haystack)? FALSE: $index);

}

?>



Example:

<?php

$test="Ralph: One of these days, Alice!!";

$look_for=":!,";   // punctuation marks



$ss = 0;

while( $answer=find_first_of($test,$look_for,$ss) ) {

  echo $answer . "\n";

  $ss = $answer+1;

 }

?>



This prints out:

5

24

31

32

daevid at daevid dot com

6 years ago


Dan Brown and I had a discussion on the PHP list about the speed difference between the popular three string searching techniques. He wrote a simple timing test, and I adapted it further. The end result is that all three are very close and not even noticeable for sets < 1M. Although, technically strpos() is about twice as fast (as the docs allude to above). Here it is for your own amusement and testing purposes.

<?php
for ($i = 0; $i < 1000000; $i++ )
    $o[] =
sprintf('%04d-%02d-%02d',rand(0000,9999),rand(00,99),rand(00,99));
#print_r($o);
echo "array of ".number_format($i)."\n";
###################################################################
$now = microtime(true);
for($i=0;$i<count($o);$i++) {
       if(preg_match('/^[0]{4,}\-/U',$o[$i])) {
               //echo "Offset #".$i." matches: ".$o[$i].PHP_EOL;
       }
}
$rank['preg_match'] = (microtime(true) - $now);
###################################################################
$later = microtime(true);
for($i=0;$i<count($o);$i++) {
        if(substr($o[$i],0,4) == "0000") {
                //echo "Offset #".$i." matches: ".$o[$i].PHP_EOL;
        }
}
$rank['substr'] = (microtime(true) - $later);
###################################################################
$after = microtime(true);
for($i=0;$i<count($o);$i++) {
        if(strpos($o[$i], '0000') === 0) {
                //echo "Offset #".$i." matches: ".$o[$i].PHP_EOL;
        }
}
$rank['strpos'] = (microtime(true) - $after);
###################################################################
asort($rank);
print_r($rank);
?>

array of 10,000
Array
(
    [strpos] => 0.00766682624817
    [substr] => 0.0116670131683
    [preg_match] => 0.0124950408936
)

array of 100,000
Array
(
    [strpos] => 0.0817799568176
    [substr] => 0.120522975922
    [preg_match] => 0.125612974167
)

array of 1,000,000
Array
(
    [strpos] => 0.805890083313
    [substr] => 1.19799995422
    [preg_match] => 1.25615906715
)

I ran out of memory with more than 1M array elements.

lairdshaw at yahoo dot com dot au

1 year ago


<?php
/*
 * A strpos variant that accepts an array of $needles - or just a string,
 * so that it can be used as a drop-in replacement for the standard strpos,
 * and in which case it simply wraps around strpos and stripos so as not
 * to reduce performance.
 *
 * The "m" in "strposm" indicates that it accepts *m*ultiple needles.
 *
 * Finds the earliest match of *all* needles. Returns the position of this match
 * or false if none found, as does the standard strpos. Optionally also returns
 * via $match either the matching needle as a string (by default) or the index
 * into $needles of the matching needle (if the STRPOSM_MATCH_AS_INDEX flag is
 * set).
 *
 * Case-insensitive searching can be specified via the STRPOSM_CI flag.
 * Note that for case-insensitive searches, if the STRPOSM_MATCH_AS_INDEX is
 * not set, then $match will be in the haystack's case, not the needle's case,
 * unless the STRPOSM_NC flag is also set.
 *
 * Flags can be combined using the bitwise or operator,
 * e.g. $flags = STRPOSM_CI|STRPOSM_NC
 */
define('STRPOSM_CI'            , 1); // CI => "case insensitive".
define('STRPOSM_NC'            , 2); // NC => "needle case".
define('STRPOSM_MATCH_AS_INDEX', 4);
function strposm($haystack, $needles, $offset = 0, &$match = null, $flags = 0) {
    // In the special case where $needles is not an array, simply wrap
    // strpos and stripos for performance reasons.
    if (!is_array($needles)) {
        $func = $flags & STRPOSM_CI ? 'stripos' : 'strpos';
        $pos = $func($haystack, $needles, $offset);
        if ($pos !== false) {
            $match = (($flags & STRPOSM_MATCH_AS_INDEX)
                      ? 0
                      : (($flags & STRPOSM_NC)
                         ? $needles
                         : substr($haystack, $pos, strlen($needles))
                        )
                      );
            return $pos;
        } else    goto strposm_no_match;
    }

    // $needles is an array. Proceed appropriately, initially by...
    // ...escaping regular expression meta characters in the needles.
    $needles_esc = array_map('preg_quote', $needles);
    // If either of the "needle case" or "match as index" flags are set,
    // then create a sub-match for each escaped needle by enclosing it in
    // parentheses. We use these later to find the index of the matching
    // needle.
    if (($flags & STRPOSM_NC) || ($flags & STRPOSM_MATCH_AS_INDEX)) {
        $needles_esc = array_map(
            function($needle) {return '('.$needle.')';},
            $needles_esc
        );
    }
    // Create the regular expression pattern to search for all needles.
    $pattern = '('.implode('|', $needles_esc).')';
    // If the "case insensitive" flag is set, then modify the regular
    // expression with "i", meaning that the match is "caseless".
    if ($flags & STRPOSM_CI) $pattern .= 'i';
    // Find the first match, including its offset.
    if (preg_match($pattern, $haystack, $matches, PREG_OFFSET_CAPTURE, $offset)) {
        // Pull the first entry, the overall match, out of the matches array.
        $found = array_shift($matches);
        // If we need the index of the matching needle, then...
        if (($flags & STRPOSM_NC) || ($flags & STRPOSM_MATCH_AS_INDEX)) {
            // ...find the index of the sub-match that is identical
            // to the overall match that we just pulled out.
            // Because sub-matches are in the same order as needles,
            // this is also the index into $needles of the matching
            // needle.
            $index = array_search($found, $matches);
        }
        // If the "match as index" flag is set, then return in $match
        // the matching needle's index, otherwise...
        $match = (($flags & STRPOSM_MATCH_AS_INDEX)
          ? $index
          // ...if the "needle case" flag is set, then index into
          // $needles using the previously-determined index to return
          // in $match the matching needle in needle case, otherwise...
          : (($flags & STRPOSM_NC)
             ? $needles[$index]
             // ...by default, return in $match the matching needle in
             // haystack case.
             : $found[0]
          )
        );
        // Return the captured offset.
        return $found[1];
    }

strposm_no_match:
    // Nothing matched. Set appropriate return values.
    $match = ($flags & STRPOSM_MATCH_AS_INDEX) ? false : null;
    return false;
}
?>

andrew dot macrobert+php at gmail dot com

1 year ago


This function finds ALL occurrences of a substring, returning an array of indexes referring to the start of each occurrence. Overlapping subtrings are not included.
<?php
function strpos_all($haystack, $needle) {
  $instances = array();

  $offset = 0;
  while(($offset = strpos($haystack, $needle, $offset)) !== FALSE) {
    $instances[] = $offset;
    $offset += strlen($needle);
  }

  return $instances;
}
?>

paul at thiswayupdesign dot co dot uk

7 years ago


I wasn't aware of the !== operator, only the === for false. I was using this code on strpos:



<?php

while( ! ($start=@strpos($source,$startTag,$end)) === false) {

  // ...

}

?>



This gave a false if the string was found at position 0, which is weird. 



However using



<?php

while(($start=@strpos($source,$startTag,$end)) !== false) {

  // ...

}

?>



Gives no such error and seems to work correctly

Lurvik

2 years ago


Don't know if already posted this, but if I did this is an improvement.

This function will check if a string contains  a needle. It _will_ work with arrays and multidimensional arrays (I've tried with a > 16 dimensional array and had no problem).

<?php
function str_contains($haystack, $needles)
{
    //If needles is an array
    if(is_array($needles))
    {
        //go trough all the elements
        foreach($needles as $needle)
        {
            //if the needle is also an array (ie needles is a multidimensional array)
            if(is_array($needle))
            {
                //call this function again
                if(str_contains($haystack, $needle))
                {
                    //Will break out of loop and function.
                    return true;
                }
                
                return false;
            }

            //when the needle is NOT an array:
                //Check if haystack contains the needle, will ignore case and check for whole words only
            elseif(preg_match("/\b$needle\b/i", $haystack) !== 0)
            {
                return true;
            }
        }
    }
    //if $needles is not an array...
    else
    {
        if(preg_match("/\b$needles\b/i", $haystack) !== 0)
        {
            return true;
        }
    }

    return false;
}
?>

Anonymous

5 years ago


Beware the mindless "if needle is not string":



# php -r 'var_dump(strpos("X1234567",5));'

bool(false)

# php -r 'var_dump(strpos("X1234567","5"));'

int(5)

m at binh dot vn

2 years ago


Using strpos can be tricky sometimes. To reuse it for one search you can use this form:

<?php
$found = (strpos($haystack, $needle) !== false);
?>

For example:

<?php
$url = "http://www.binh.vn";
$found = (strpos($url, 'http') !== false);
if ($found) echo "Found http";
?>

Clearly we see that the position will be 0 but the $found will be true and so we can use more than one time of if ($found) which is much easier.

To further reuse it we could make a very short function:
<?php 
function found($haystack, $needle) {
  return (strpos($haystack, $needle) !== false);
}
?>

Wonder why php didn't have such function for easier use?

mail at nikha dot org

1 year ago


What the manual says about "if $needle is not a string" is confusing.

in fact, strpos() compares strings, and nothing else. 

Example:
$haystack = "123456789";

$needle = 2;
strpos($haystack, $needle) returns boolean false
$needle = "2";
strpos($haystack, $needle) returns 1;

My real life problem were timestamps. I had a list of timestamps like this: "!<timestamp0>!<timestamp1>!<timestamp2>..." Then I tried to find out, wheter an actualy by "mktime()" generated timestamp is found in this list or not. But strpos() returned always boolean 0, because mktime() results are integers.

It worked only like this: 
strpos($timestamp_list, strval($mktime_result))
 
may be helpfull for others...
Niklaus

kiipa at live dot com

2 years ago


So I needed a function to check if a string contains a string. But that also works with arrays. And multidimensional arrays.

Well commented, because I'm sharing the source I use this in.

<?php
private static $found;
//Sees if a string contains another string, WORKS WITH 2D ARRAYS! Returns true or false.
public static function strcont($haystack, $needles)
{
    //If needles is an array
    if(is_array($needles))
    {
        //go trough all the elements
        foreach($needles as $needle)
        {
            //if the needle is also an array (ie needles is a multidimensional array)
            if(is_array($needle))
            {
                //call this function again
                static::strcont($haystack, $needle);
            }
            //when the needle is NOT an array:
            elseif(strpos($haystack, $needle) !== false)
            {
                //Set the bool to true (DO NOT CHANGE TO return true). IT WILL NOT WORK!
                static::$found = true;
            }
        }

        //Because we only set the bool if we found something we'll check if the bool is set.
        if(isset(static::$found))
        {
            //Then return true.
            return true;
        }
        
        return false;
    }
    //If the needles is not an array (this function can be used as strpos...)
    else
    {
        if(strpos($haystack, $needles) !== false)
        {
            return true;
        }
        
        return falsE;
    }
}    
?>

newartix at mail dot ru

1 year ago


Extend (ohcc at 163 dot com)s comment:

Be careful when the $haystack or $needle parameter is an integer.
If you are not sure of its type, you should  convert it into a string.
<?php
    var_dump(strpos(12345,1));//false
    var_dump(strpos(12345,'1'));//0
    var_dump(strpos('12345',1));//false
    var_dump(strpos('12345','1'));//0
    $a = 12345;
    $b = 1;
    var_dump(strpos(strval($a),strval($b)));//0
    var_dump(strpos((string)$a,(string)$b));//0    
    
    // and wait for interesting... CentOS 6.5 PHP-FPM 5.4.35
    var_dump(strpos('mrwagon',626));//1      tadaaam!
?>

strpos

Description

Parameters

Return Values

Examples

Notes

See Also

User Contributed Notes