$re = '/([2-9](?!11)[0-9]{2})/m';
$str = 'These would be valid area codes: 414, 608, 920, 319, 715
These would NOT be valid: 023, 123, 411, 611, 811, 911';
preg_match_all($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