$re = '/^(?<Monthswith31>31(?<s1>\/|\.|-)(0?[13578]|1[02]|(Jan|Mar|May|Jul|Aug|Oct|Dec))\g<s1>(?<Year>19[0-9][0-9]|200[0-7]))$|^(?<Monthswith29or30>(29|30)(?<s2>\/|\.|-)(0?[1,3-9]|1[0-2]|(Jan|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec))\g<s2>(?<Year2>19[0-9][0-9]|200[0-7]))$|^(?<Allmonthswith28>(0?[1-9]|1[0-9]|2[0-8])(?<s3>\/|\.|-)(0?[1-9]|1[0-2]|(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec))\g<s3>(?<Year3>19[0-9][0-9]|200[0-7]))$|^(?<FebLeapYears>29(?<s4>\/|\.|-)(0?2|Feb)\g<s4>(19([02468][048]|[13579][26])|200[04]))$/m';
$str = '02/Apr/2006
23/10/1996
13/10/2000
Right Ones
28/05/2000
01/01/2000
1/1/2000
01/Jan/2000
31/01/
31/Jan/2000
31.Jan.2000
31-Jan-2012
30/Mar/2000
29/Apr/2000
29/10/2000
29/02/2000
20/Apr/1983
28/02/2000
01/1/2000
01/Jan/2000
01/1/01
01/Jan/01
29/02/2000
29/Feb/2000
01/01/2020 #1st Jan
07/03/2020 #3 July
12/2/2020 #2 December
23/4/2020 #23 April
Wrong Ones
31/04/2000
29/Feb/2001
13/13/2000
30/Feb/2000
25/February/2000
32/01/2000
32/Jan/2000
';
preg_match_all($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