PHP Manual
preg_match
(PHP 4, PHP 5) preg_match — Perform a regular expression match
Description
int preg_match
( string $pattern
, string $subject
[, array &$matches
[, int $flags = 0
[, int $offset = 0
]]] )
Parameters
-
pattern
-
The pattern to search for, as a string.
-
subject
-
The input string.
-
matches
-
If matches is provided, then it is filled with
the results of search. $matches[0] will contain the
text that matched the full pattern, $matches[1]
will have the text that matched the first captured parenthesized
subpattern, and so on.
-
flags
-
flags can be the following flag:
-
PREG_OFFSET_CAPTURE
-
If this flag is passed, for every occurring match the appendant string
offset will also be returned. Note that this changes the value of
matches into an array where every element is an
array consisting of the matched string at offset 0
and its string offset into subject at offset
1.
-
offset
-
Normally, the search starts from the beginning of the subject string.
The optional parameter offset can be used to
specify the alternate place from which to start the search (in bytes).
Note:
Using offset is not equivalent to passing
substr($subject, $offset) to
preg_match() in place of the subject string,
because pattern can contain assertions such as
^, $ or
(?<=x). Compare:
Return Values
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.
Examples
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.htm", $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:
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
)
Notes
Tip
Do not use preg_match() if you only want to check if
one string is contained in another string. Use
strpos() or strstr() instead as
they will be faster.
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