$re = '/(0[1-9]|[12]\d|3[0-1])[\./]([0[1-9]|1[0-2])[\./](196[1-9]|19[7-9]\d|20\d\d|2100)/m';
$str = '01.12.1990
04.05.2000
31.12.2010
31.12.1980
31.12.1989
31.12.1999';
preg_match_all($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