preg_filter

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

    preg_filter — Perform 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
)

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    User Contributed Notes 3 notes

    up
    10
    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
    7
    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
    3
    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 ;

    }

    }
    ?>
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