$re = '/(?P<Date>(?:(?:(?P<Day>\d{1,2})[ /\.]+)?(?P<Month>January|February|March|April|May|June|July|August|September|October|November|December|\d{1,2})[ /\.]+)?(?P<Year>\d{4}|(?(Month)\d{2}|(?P<Age>\d{2}))))\b/mi';
$str = 'a 15/01/2012
13/54
34';
preg_match_all($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