$re = '/((([12]{1}\d\d)|(1-9]\d)|([1-9]))[\.]){3}(([12]{1}\d\d)|([1-9]\d)|([1-9]))/';
$str = '1.2.3.4';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($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