$re = '/^(20[12]\d)(0[1-9]|1[012])(0[1-9]|[12]\d|3[01])_([01]\d|2[0-3])[0-5]\d[0-5]\d-\w+\.sql$/';
$str = 'DYO_STUS_20150120T143814.xml';
preg_match($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