PHP preg_match_all() Function: Usage, Parameters, and Examples

The preg_match_all() function performs a global regular‑expression match on a subject string, returning all matches in an array.

Signature:

int preg_match_all(string $pattern, string $subject, array &$matches, int $flags = 0, int $offset = 0)

Parameters: $pattern – the regex pattern to search for. $subject – the input string. $matches – an output array that receives the matches; its ordering is controlled by $flags. $flags – optional flags such as PREG_PATTERN_ORDER or PREG_SET_ORDER (cannot be combined). $offset – optional byte offset to start the search.

Return value: the number of full pattern matches (or FALSE on error).

Example 1 – Matching phone numbers:

<?php
preg_match_all("/\(?(\d{3})?\)?(?(1)[\-\s])\d{3}-\d{4}/x", "Call 555-1212 or 1-800-555-1212", $phones);
print_r($phones);
?>

Output:

Array
(
    [0] => Array
        (
            [0] => 555-1212
            [1] => 1-800-555-1212
        )
)

Example 2 – Extracting HTML tags and their contents:

<?php
$html = "<b>bold text</b><a href=howdy.html>click me</a>";
preg_match_all("/(<([\w]+)[^>]*>)(.*?)(<\/\\2>)/", $html, $matches, PREG_SET_ORDER);
foreach ($matches as $val) {
    echo "matched: " . $val[0] . "
";
    echo "part 1: " . $val[1] . "
";
    echo "part 2: " . $val[2] . "
";
    echo "part 3: " . $val[3] . "
";
}
?>

Output (simplified):

matched: <b>bold text</b>
part 1: <b>
part 2: bold text
part 3: </b>
matched: <a href=howdy.html>click me</a>
part 1: <a href=howdy.html>
part 2: click me
part 3: </a>

Example 3 – Using named sub‑patterns:

<?php
$str = <<<FOO
a: 1
b: 2
c: 3
FOO;
preg_match_all('/(?P<name>\w+): (?P<digit>\d+)/', $str, $matches);
print_r($matches);
?>

Output:

Array
(
    [0] => Array
        (
            [0] => a: 1
            [1] => b: 2
            [2] => c: 3
        )
    [name] => Array
        (
            [0] => a
            [1] => b
            [2] => c
        )
    [digit] => Array
        (
            [0] => 1
            [1] => 2
            [2] => 3
        )
)