PHP preg_match_all function

preg_match_all

(PHP 3 >= 3.0.9, PHP 4, PHP 5)

preg_match_all -- Perform a global regular expression matchDescriptionint 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.

Parameters

pattern

The pattern to search for, as a string.

subject

The input string.

matches

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.

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.

PLAIN TEXT

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.

PLAIN TEXT

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 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.

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.

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

VersionDescription4.3.3 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.

PLAIN 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)

PLAIN TEXT

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[3] . "\n";
echo "part 3: " . $val[4] . "\n\n";
}