$re = '/^L1(?:,(\d+)){3}/';
$str = 'L1,3,5,0,5,80,40,31,0,0,0,0,512,412,213,900';
preg_match($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