$re = '/^\d{3,5}([- ]?\d{4})?$/m';
$str = '27364
2839
37567-2839
28448 3950
3847933
28448 3953
3
3858049494
38494 4
49500-
49500-35
49500-35-34
-32893-3429
';
preg_match_all($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