(PHP 4, PHP 5)
preg_match — Perform a regular expression match
Searches subject for a match to the regular expression given in pattern.
The pattern to search for, as a string.
The input string.
If matches is provided, then it is filled with the results of search. $matches[0] will contain the text that matched the full pattern, $matches[1] will have the text that matched the first captured parenthesized subpattern, and so on.
flags can be the following flag:
Normally, the search starts from the beginning of the subject string. The optional parameter offset can be used to specify the alternate place from which to start the search (in bytes).
Note: Using offset is not equivalent to passing substr($subject, $offset) to preg_match() in place of the subject string, because pattern can contain assertions such as ^, $ or (?<=x). Compare:
<?php
$subject = "abcdef";
$pattern = '/^def/';
preg_match($pattern, $subject, $matches, PREG_OFFSET_CAPTURE, 3);
print_r($matches);
?>The above example will output:
Array ( )while this example
<?php
$subject = "abcdef";
$pattern = '/^def/';
preg_match($pattern, substr($subject,3), $matches, PREG_OFFSET_CAPTURE);
print_r($matches);
?>will produce
Array ( [0] => Array ( [0] => def [1] => 0 ) )
preg_match() returns the number of times pattern matches. That will be either 0 times (no match) or 1 time because preg_match() will stop searching after the first match. preg_match_all() on the contrary will continue until it reaches the end of subject. preg_match() returns FALSE if an error occurred.
| Version | Description |
|---|---|
| 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 |
| 4.3.0 | The flags parameter was added |
Example #1 Find the string of text "php"
<?php
// The "i" after the pattern delimiter indicates a case-insensitive search
if (preg_match("/php/i", "PHP is the web scripting language of choice.")) {
echo "A match was found.";
} else {
echo "A match was not found.";
}
?>
Example #2 Find the word "web"
<?php
/* The \b in the pattern indicates a word boundary, so only the distinct
* word "web" is matched, and not a word partial like "webbing" or "cobweb" */
if (preg_match("/\bweb\b/i", "PHP is the web scripting language of choice.")) {
echo "A match was found.";
} else {
echo "A match was not found.";
}
if (preg_match("/\bweb\b/i", "PHP is the website scripting language of choice.")) {
echo "A match was found.";
} else {
echo "A match was not found.";
}
?>
Example #3 Getting the domain name out of a URL
<?php
// get host name from URL
preg_match('@^(?:http://)?([^/]+)@i',
"http://www.php.net/index.html", $matches);
$host = $matches[1];
// get last two segments of host name
preg_match('/[^.]+\.[^.]+$/', $host, $matches);
echo "domain name is: {$matches[0]}\n";
?>
The above example will output:
domain name is: php.net
Example #4 Using named subpattern
<?php
$str = 'foobar: 2008';
preg_match('/(?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('/(?<name>\w+): (?<digit>\d+)/', $str, $matches);
print_r($matches);
?>
The above example will output:
Array
(
[0] => foobar: 2008
[name] => foobar
[1] => foobar
[digit] => 2008
[2] => 2008
)