$re = '/(1[0-2]|[1-9])[\s\\\\\/\.-](3[0-1]|[1-2][0-9]|[1-9])/';
$str = 'Random Input
//
apples
100
10
Invalid Dates
1/0
1/1
1/9
1/10
1/19
1/20
1/29
1/30
1/31
1/32
Separators
10-10
10.10
10\\10
10/10
10a10
10%10
';
preg_match_all($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