$re = '/^\d{3}(?:-\d{3})?(?:\s*(?:,|and|or)\s*\d{3}(?:-\d{3})?)*(?=,|$)/m';
$str = '345
346-348
234,235,236,237-239
234, 235, 236, 237-239
234,234, 236 and 237-239
234,234, 236 or 237-239
3454
454,4567 (match only 454)';
preg_match_all($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