preg_match

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Description

int preg_match_all ( string pattern, string subject, array &matches [, int flags [, int offset]])

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.

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";
?>

This example will produce:

<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";
?>

This example will produce:

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

In this case, $matches[0] is the first set of matches, and $matches[0][0] has text matched by full pattern, $matches[0][1] has text matched by first subpattern and so on. Similarly, $matches[1] is the second set of matches, etc.

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 return value in 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. This flag is available since PHP 4.3.0 .

If no order flag is given, PREG_PATTERN_ORDER is assumed.

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. The offset parameter is available since PHP 4.3.3.

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.

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

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 = "bold text<a href=howdy.html>click me</a>"; preg_match_all("/(<([\w]+)[^>]*>)(.*)(<\/\\2>)/", $html, $matches); for ($i=0; $i< count($matches[0]); $i++) { echo "matched: " . $matches[0][$i] . "\n"; echo "part 1: " . $matches[1][$i] . "\n"; echo "part 2: " . $matches[3][$i] . "\n"; echo "part 3: " . $matches[4][$i] . "\n\n"; } ?>
This example will produce:
matched: bold text part 1: part 2: bold text part 3: matched: <a href=howdy.html>click me</a> part 1: <a href=howdy.html> part 2: click me part 3: </a>