preg_match_all

(PHP 4, PHP 5)

preg_match_all — Perform a global regular expression match

Description

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

Searches subject for all matches to the regular expression given in pattern and puts them in matches in the order specified by flags.

After the first match is found, the subsequent searches are continued on from end of the last match.

Parameters

pattern

The pattern to search for, as a string.

subject

The input string.

matches

Array of all matches in multi-dimensional array ordered according to flags.

flags

Can be a combination of the following flags (note that it doesn't make sense to use PREG_PATTERN_ORDER together with PREG_SET_ORDER):

PREG_PATTERN_ORDER

Orders results so that $matches[0] is an array of full pattern matches, $matches[1] is an array of strings matched by the first parenthesized subpattern, and so on.

<?php
preg_match_all("|<[^>]+>(.*)</[^>]+>|U",
    "<b>example: </b><div align=left>this is a test</div>",
    $out, PREG_PATTERN_ORDER);
echo $out[0][0] . ", " . $out[0][1] . "\n";
echo $out[1][0] . ", " . $out[1][1] . "\n";
?>

The above example will output:

<b>example: </b>, <div align=left>this is a test</div>
example: , this is a test

So, $out[0] contains array of strings that matched full pattern, and $out[1] contains array of strings enclosed by tags.

PREG_SET_ORDER

Orders results so that $matches[0] is an array of first set of matches, $matches[1] is an array of second set of matches, and so on.

<?php
preg_match_all("|<[^>]+>(.*)</[^>]+>|U",
    "<b>example: </b><div align=\"left\">this is a test</div>",
    $out, PREG_SET_ORDER);
echo $out[0][0] . ", " . $out[0][1] . "\n";
echo $out[1][0] . ", " . $out[1][1] . "\n";
?>

The above example will output:

<b>example: </b>, example:
<div align="left">this is a test</div>, this is a test

PREG_OFFSET_CAPTURE

If this flag is passed, for every occurring match the appendant string offset will also be returned. Note that this changes the value of matches into an array where every element is an array consisting of the matched string at offset 0 and its string offset into subject at offset 1.

If no order flag is given, PREG_PATTERN_ORDER is assumed.

offset

Normally, the search starts from the beginning of the subject string. The optional parameter offset can be used to specify the alternate place from which to start the search (in bytes).

Note:

Using offset is not equivalent to passing substr($subject, $offset) to preg_match_all() in place of the subject string, because pattern can contain assertions such as ^, $ or (?<=x). See preg_match() for examples.

Return Values

Returns the number of full pattern matches (which might be zero), or FALSE if an error occurred.

Changelog

Version Description
5.4.0 The matches parameter became optional.
5.3.6 Returns FALSE if offset is higher than subject length.
5.2.2 Named subpatterns now accept the syntax (?<name>) and (?'name') as well as (?P<name>). Previous versions accepted only (?P<name>).
4.3.3 The offset parameter was added
4.3.0 The PREG_OFFSET_CAPTURE flag was added

Examples

Example #1 Getting all phone numbers out of some text.

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

Example #2 Find matching HTML tags (greedy)

<?php
// The \\2 is an example of backreferencing. This tells pcre that
// it must match the second set of parentheses in the regular expression
// itself, which would be the ([\w]+) in this case. The extra backslash is
// required because the string is in double quotes.
$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] . "\n";
    echo "part 1: " . $val[1] . "\n";
    echo "part 2: " . $val[2] . "\n";
    echo "part 3: " . $val[3] . "\n";
    echo "part 4: " . $val[4] . "\n\n";
}
?>

The above example will output:

matched: <b>bold text</b>
part 1: <b>
part 2: b
part 3: bold text
part 4: </b>

matched: <a href=howdy.html>click me</a>
part 1: <a href=howdy.html>
part 2: a
part 3: click me
part 4: </a>

Example #3 Using named subpattern

<?php

$str = <<<FOO
a: 1
b: 2
c: 3
FOO;

preg_match_all('/(?P<name>\w+): (?P<digit>\d+)/', $str, $matches);

/* This also works in PHP 5.2.2 (PCRE 7.0) and later, however 
 * the above form is recommended for backwards compatibility */
// preg_match_all('/(?<name>\w+): (?<digit>\d+)/', $str, $matches);

print_r($matches);

?>

The above example will output:

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

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

    [1] => Array
        (
            [0] => a
            [1] => b
            [2] => c
        )

    [digit] => Array
        (
            [0] => 1
            [1] => 2
            [2] => 3
        )

    [2] => Array
        (
            [0] => 1
            [1] => 2
            [2] => 3
        )

)

See Also