PHP preg_match() Function: Syntax, Parameters, Return Values, and Examples

preg_match() executes a regular expression match on a subject string.

Parameters : string $pattern – the regex pattern. string $subject – the input string. array &$matches – optional array filled with the results. int $flags = 0 – optional flags such as PREG_OFFSET_CAPTURE. int $offset = 0 – optional start offset.

Return value : number of matches (0 or 1) or FALSE on error.

Example 1 demonstrates a case‑insensitive search for the word “PHP”.

<?php
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 uses word boundaries \b to match only the whole word “web”.

<?php
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.";
}
?>

Example 3 extracts the host name from a URL.

<?php
preg_match('@^(?:http://)?([^/]+)@i', "http://www.php.net/index.html", $matches);
$host = $matches[1];
echo "domain name is: $host
";
?>

Example 4 shows named sub‑patterns to capture a name and a number.

<?php
$str = 'foobar: 2008';
preg_match('/(?P<name>\w+): (?P<digit>\d+)/', $str, $matches);
print_r($matches);
?>