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# preg_match

(PHP 3>= 3.0.9, PHP 4 )

preg_match -- Perform a regular expression match

## Description

int preg_match ( string pattern, string subject [, array matches [, int flags]])

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

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:

PREG_OFFSET_CAPTURE

  If this flag is set, for every occuring match the appendant string offset will also be returned. Note that this changes the return value in an array where every element is an array consisting of the matched string at offset `0` and it's string offset into `subject` at offset `1`. This flag is available since `PHP` 4.3.0 .

The `flags` parameter is available since `PHP` 4.3.0 .

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 occured.

Example 1. Find the string of text "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.")) {
        print "A match was found.";
    } else {
        print "A match was not found.";
    }

Example 2. find the word "web"

    // 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.")) {
        print "A match was found.";
    } else {
        print "A match was not found.";
    }
    if (preg_match ("/\bweb\b/i", "PHP is the website scripting language of choice.")) {
        print "A match was found.";
    } else {
        print "A match was not found.";
    }

Example 3. Getting the domain name out of a URL

    // get host name from URL
    preg_match("/^(http:\/\/)?([^\/]+)/i",
    "http://www.php.net/index.html", $matches);
    $host = $matches[2];
    // get last two segments of host name
    preg_match("/[^\.\/]+\.[^\.\/]+$/",$host,$matches);
    echo "domain name is: ".$matches[0]."\n";

This example will produce:

    domain name is: php.net

See also preg_match_all(), preg_replace(), and preg_split().

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