$re = '/^[1-31].[1-12]/m';
$str = '13.11.1986
01.01.1999
31.12.2020
15.06.2000
01.01.1920
############### Not valid ###########################
31.12.1919
12.13.1985
1.1.2005
1.5.86
';
preg_match_all($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