$re = '/^(\w{8})(\w{8})(\w{4})(\w{8})(\w{39})$/';
$str = '49cd0d18000100000069543ace68000000000000000000000000000000000000000';
preg_match($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