preg_filter

(PHP 5 >= 5.3.0, PHP 7, PHP 8)

preg_filterPerform a regular expression search and replace

Description

preg_filter(
    string|array $pattern,
    string|array $replacement,
    string|array $subject,
    int $limit = -1,
    int &$count = null
): string|array|null

preg_filter() is identical to preg_replace() except it only returns the (possibly transformed) subjects where there was a match. For details about how this function works, read the preg_replace() documentation.

Parameters

Parameters are described in the documentation for preg_replace().

Return Values

Returns an array if the subject parameter is an array, or a string otherwise.

If no matches are found or an error occurred, an empty array is returned when subject is an array or null otherwise.

Errors/Exceptions

If the regex pattern passed does not compile to a valid regex, an E_WARNING is emitted.

Examples

Example #1 Example comparing preg_filter() with preg_replace()

<?php
$subject
= array('1', 'a', '2', 'b', '3', 'A', 'B', '4');
$pattern = array('/\d/', '/[a-z]/', '/[1a]/');
$replace = array('A:$0', 'B:$0', 'C:$0');

echo
"preg_filter returns\n";
print_r(preg_filter($pattern, $replace, $subject));

echo
"preg_replace returns\n";
print_r(preg_replace($pattern, $replace, $subject));
?>

The above example will output:

preg_filter returns
Array
(
    [0] => A:C:1
    [1] => B:C:a
    [2] => A:2
    [3] => B:b
    [4] => A:3
    [7] => A:4
)
preg_replace returns
Array
(
    [0] => A:C:1
    [1] => B:C:a
    [2] => A:2
    [3] => B:b
    [4] => A:3
    [5] => A
    [6] => B
    [7] => A:4
)

See Also

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User Contributed Notes 6 notes

up
9
forsoap at gmail dot com
7 years ago
For those who read manual not in English and figure out that example code returns not the same result as in documentation

You need put in example patter modifier "u" to get same result:

<?php
$subject
= array('1', 'а', '2', 'б', '3', 'А', 'Б', '4');
// Added "u"
$pattern = array('/\d/u', '/[а-я]/u', '/[1а]/u');
$replace = array('А:$0', 'Б:$0', 'В:$0');
?>
up
5
bienvenunet at yahoo dot com
6 years ago
If you don't want to actually replace the matches, just filter the array to them, make the replacement parameter '$0'.

<?php
$subject
= array('1', 'a', '2', 'b', '3', 'A', 'B', '4');
$result = preg_filter('/\d/', '$0', $subject);  // ['1','2','3','4']
?>
up
0
sajina_99 at hotmail dot de
12 years ago
As I had to work with PHP5.2.X and needed preg_filter I wrote a quick and dirty workaround.

<?php
 
if (!function_exists('preg_filter')) {
 
    function
preg_filter($pattern, $replace, $subject, $limit = -1 , &$count = null) {
   
      if(!
is_array($subject)) {
       
$noArray = 1 ;
       
$subject = array($subject);
      }

     
$preg = preg_replace($pattern, $replace, $subject, $limit,  &$count);

     
$diff = array_diff($preg, $subject);
     
      if(
$noArray == 1) $diff = implode($diff) ;

      return
$diff ;
     
    }
   
  }
?>
up
-24
MrBertie
13 years ago
Another way to filter an array, and simply return the matching items: preg_grep!
up
-23
fgmhhfg at gmail dot com
10 years ago
As for the php 5.5.3 version, the example  turn out like:
Array
(
       [0] => A:1
       [1] => B:a
       ...
)
up
-35
Anonymous
10 years ago
As for the php 5.5.3 version, the example will turn out like:
Array
(
       [0]=>A:1
       [1]=>B:a
       ...
)
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