$re = '/^((([0-9])|(1([0-9]{1,2}))|25[0-5]|(2[0-4][0-9])|(2([0-9]{0,1})))\.){3}\2$/m';
$str = '';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php