preg_filter(3) [php man page]
PREG_FILTER(3) 1 PREG_FILTER(3) preg_filter - Perform a regular expression search and replace SYNOPSIS
mixed preg_filter (mixed $pattern, mixed $replacement, mixed $subject, [int $limit = -1], [int &$count]) DESCRIPTION
preg_filter(3) is identical to preg_replace(3) except it only returns the (possibly transformed) subjects where there was a match. For details about how this function works, read the preg_replace(3) documentation. RETURN VALUES
Returns an array if the $subject parameter is an array, or a string otherwise. If no matches are found or an error occurred, an empty array is returned when $subject is an array or NULL otherwise. EXAMPLES
Example #1 Example comparing preg_filter(3) with preg_replace(3) <?php $subject = array('1', 'a', '2', 'b', '3', 'A', 'B', '4'); $pattern = array('/d/', '/[a-z]/', '/[1a]/'); $replace = array('A:$0', 'B:$0', 'C:$0'); echo "preg_filter returns "; print_r(preg_filter($pattern, $replace, $subject)); echo "preg_replace returns "; print_r(preg_replace($pattern, $replace, $subject)); ?> The above example will output: preg_filter returns Array ( [0] => A:C:1 [1] => B:C:a [2] => A:2 [3] => B:b [4] => A:3 [7] => A:4 ) preg_replace returns Array ( [0] => A:C:1 [1] => B:C:a [2] => A:2 [3] => B:b [4] => A:3 [5] => A [6] => B [7] => A:4 ) SEE ALSO
PCRE Patterns, preg_quote(3), preg_replace(3), preg_replace_callback(3), preg_grep(3), preg_last_error(3). PHP Documentation Group PREG_FILTER(3)
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PREG_MATCH(3) 1 PREG_MATCH(3) preg_match - Perform a regular expression match SYNOPSIS
int preg_match (string $pattern, string $subject, [array &$matches], [int $flags], [int $offset]) DESCRIPTION
Searches $subject for a match to the regular expression given in $pattern. PARAMETERS
o $pattern - The pattern to search for, as a string. o $subject - The input string. o $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. o $flags -$flags can be the following flag: o 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. o $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(3) 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 ) ) RETURN VALUES
preg_match(3) returns 1 if the $pattern matches given $subject, 0 if it does not, or FALSE if an error occurred. Warning This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE. Please read the section on Booleans for more information. Use the === operator for testing the return value of this function. CHANGELOG
+--------+---------------------------------------------------+ |Version | | | | | | | Description | | | | +--------+---------------------------------------------------+ | 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>). | | | | +--------+---------------------------------------------------+ 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 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("/web/i", "PHP is the web scripting language of choice.")) { echo "A match was found."; } else { echo "A match was not found."; } if (preg_match("/web/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]} "; ?> 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 ) NOTES
Tip Do not use preg_match(3) if you only want to check if one string is contained in another string. Use strpos(3) or strstr(3) instead as they will be faster. SEE ALSO
PCRE Patterns, preg_quote(3), preg_match_all(3), preg_replace(3), preg_split(3), preg_last_error(3). PHP Documentation Group PREG_MATCH(3)