$re = '/^(?=[^A-Z\n]*[A-Z])(?=[^0-9\n]*[0-9])[0-9 A-Z]*$/m';
$str = '3 T1F ROHITE01WMILWI16
3 T1F ROHITHE01WMILwI16
3 T1F ROHITHE01WMIL.I16
1234
aaaa
T1F ROHITHE01WMILWI16';
preg_match_all($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