preg_match

(PHP 4, PHP 5, PHP 7)
Perform a regular expression match
int preg_match ( string $pattern, string $subject [, array &$matches [, int $flags = 0 [, int $offset = 0 ]]] )

Searches subject for a match to the regular expression given in pattern.

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:

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:

<?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
        )

)
Returns:

preg_match() 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:
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:
The above example will output:

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);
?>

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
        )

)
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.";
}
?>

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.";
}
?>

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
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
)
See also:

PCRE Patterns -

preg_quote() -

preg_match_all() -

preg_replace() -

preg_split() -

preg_last_error() -

doc_php
2016-02-24 16:12:19
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