PHP Find all occurrences of a substring in a string

Question

I need to parse an HTML document and to find all occurrences of string asdf in it.

I currently have the HTML loaded into a string variable. I would just like the character position so I can loop through the list to return some data after the string.

The strpos function only returns the first occurrence. How about returning all of them?

score 106 · Accepted Answer · edited May 12 '15 at 13:05

106

Without using regex, something like this should work for returning the string positions:

$html = "dddasdfdddasdffff";
$needle = "asdf";
$lastPos = 0;
$positions = array();

while (($lastPos = strpos($html, $needle, $lastPos))!== false) {
    $positions[] = $lastPos;
    $lastPos = $lastPos + strlen($needle);
}

// Displays 3 and 10
foreach ($positions as $value) {
    echo $value ."<br />";
}

edited May 12 '15 at 13:05

trejder

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answered Apr 01 '13 at 04:01

Adam Plocher

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14

Please be careful using assignments in `if` statements. In this case, your `while` loop didn't work for position `0`. I've updated your answer. – Robbert Nov 06 '13 at 12:57
9

Excelent fix, but for those needing to find special characters (é, ë, ...) replace the strpos with mb_strpos, otherwise it won't work – Brentg Jun 22 '16 at 13:44
All of those who will reuse this code be careful because your needle may be something like "dd" in which case $lastPos should only increase by one inside the while loop. – assensi Aug 07 '20 at 09:52

Salman A · Answer 2 · 2014-12-06T15:40:20.247

You can call the strpos function repeatedly until a match is not found. You must specify the offset parameter.

Note: in the following example, the search continues from the next character instead of from the end of previous match. According to this function, aaaa contains three occurrences of the substring aa, not two.

function strpos_all($haystack, $needle) {
    $offset = 0;
    $allpos = array();
    while (($pos = strpos($haystack, $needle, $offset)) !== FALSE) {
        $offset   = $pos + 1;
        $allpos[] = $pos;
    }
    return $allpos;
}
print_r(strpos_all("aaa bbb aaa bbb aaa bbb", "aa"));

Output:

Array
(
    [0] => 0
    [1] => 1
    [2] => 8
    [3] => 9
    [4] => 16
    [5] => 17
)

score 18 · Answer 3 · answered Nov 14 '13 at 11:42

18

Its better to use substr_count . Check out on php.net

answered Nov 14 '13 at 11:42

Nirmal Ram

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this only gives you the count, not their positions as the question asked – DaveB Jul 07 '16 at 12:18
2

"This function doesn't count overlapped substrings." For string 'abababa' when you look 'aba' it will count only 2 times not 3 – R Picheta Sep 29 '16 at 21:27

score 4 · Answer 4 · answered Mar 08 '14 at 15:32

4

function getocurence($chaine,$rechercher)
        {
            $lastPos = 0;
            $positions = array();
            while (($lastPos = strpos($chaine, $rechercher, $lastPos))!== false)
            {
                $positions[] = $lastPos;
                $lastPos = $lastPos + strlen($rechercher);
            }
            return $positions;
        }

answered Mar 08 '14 at 15:32

Ryodo

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Code-only answers are low value on StackOverflow because they do very little to educate the OP and future readers. Please edit your answer with the intent to educate thousands of future SO readers and the OP. – mickmackusa Apr 01 '18 at 11:53

score 3 · Answer 5 · edited May 12 '15 at 13:03

3

Use preg_match_all to find all occurrences.

preg_match_all('/(\$[a-z]+)/i', $str, $matches);

For further reference check this link.

edited May 12 '15 at 13:03

trejder

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answered Apr 01 '13 at 04:04

웃웃웃웃웃

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He's looking for string positions, not just matches. Also he's looking to match "asdf", not [a-z]... – Adam Plocher Apr 01 '13 at 04:16

Kach · Answer 6 · 2014-02-04T17:14:51.637

This can be done using strpos() function. The following code is implemented using for loop. This code is quite simple and pretty straight forward.

<?php

$str_test = "Hello World! welcome to php";

$count = 0;
$find = "o";
$positions = array();
for($i = 0; $i<strlen($str_test); $i++)
{
     $pos = strpos($str_test, $find, $count);
     if($pos == $count){
           $positions[] = $pos;
     }
     $count++;
}
foreach ($positions as $value) {
    echo '<br/>' .  $value . "<br />";
}

?>

score 2 · Answer 7 · edited May 14 '20 at 15:18

Salman A has a good answer, but remember to make your code multibyte-safe. To get correct positions with UTF-8, use mb_strpos instead of strpos:

function strpos_all($haystack, $needle) {
    $offset = 0;
    $allpos = array();
    while (($pos = mb_strpos($haystack, $needle, $offset)) !== FALSE) {
        $offset   = $pos + 1;
        $allpos[] = $pos;
    }
    return $allpos;
}
print_r(strpos_all("aaa bbb aaa bbb aaa bbb", "aa"));

score 1 · Answer 8 · answered May 08 '21 at 22:59

Another solution is to use explode():

public static function allSubStrPos($str, $del)
{
    $searchArray = explode($del, $str);
    unset($searchArray[count($searchArray) - 1]);
    $positionsArray = [];
    $index = 0;
    foreach ($searchArray as $i => $s) {
        array_push($positionsArray, strlen($s) + $index);
        $index += strlen($s) + strlen($del);
    }
    return $positionsArray;
}

score 0 · Answer 9 · answered Apr 10 '20 at 16:07

0

Simple strpos_all() function.

function strpos_all($haystack, $needle_regex)
{
    preg_match_all('/' . $needle_regex . '/', $haystack, $matches, PREG_OFFSET_CAPTURE);
    return array_map(function ($v) {
        return $v[1];
    }, $matches[0]);
}

Usage: Simple string as needle.

$html = "dddasdfdddasdffff";
$needle = "asdf";

$all_positions = strpos_all($html, $needle);
var_dump($all_positions);

Output:

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

Or with regex as needle.

$html = "dddasdfdddasdffff";
$needle = "[d]{3}";

$all_positions = strpos_all($html, $needle);
var_dump($all_positions);

Output:

array(2) {
  [0]=>
  int(0)
  [1]=>
  int(7)
}

answered Apr 10 '20 at 16:07

Jalo

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Using regular expressions to look for a substring is not a good approach. Of course you can do it but regex is for more complex scenarios. Using `strpos` is much simpler in this case and does the job. – omar jayed Apr 11 '20 at 04:44
1

A warning about getting the offset in a string that may have multibyte characters: [preg_match and UTF-8 in PHP](https://stackoverflow.com/q/1725227/2943403) – mickmackusa Mar 15 '22 at 03:36

score 0 · Answer 10 · answered Jul 20 '20 at 17:01

<?php
$mainString = "dddjmnpfdddjmnpffff";
$needle = "jmnp";
$lastPos = 0;
$positions = array();

while (($lastPos = strpos($html, $needle, $lastPos))!== false) {
    $positions[] = $lastPos;
    $lastPos = $lastPos + strlen($needle);
}

// Displays 3 and 10
foreach ($positions as $value) {
    echo $value ."<br />";
}
?>

PHP Find all occurrences of a substring in a string

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