$re = '/^(?:[0-3]|[6-9])[0-9]*|[54]\d{4,}$/m';
$str = '1500
26489
212
15849
5000
5001
4584
2402
5191981
4618916
6540
4500
45000
9999999
4001
4000
3999
5999
6000';
preg_match_all($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