$re = '/((^3\.(0[13578]|1[2])(\.[0-9]{4})|^28\.02\.([0-9]{4}))|(30\.(0[469]|11)(\.[0-9]{4})|^[0-2][0-9]\.(0[13578]|1[02])(\.[0-9]{4})))$/m';
$str = '26.01.2020
10.12.2020
';
preg_match_all($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