$re = '/^[a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9]-[a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9]-.+$/m';
$str = 'UEF-KH1-errttz
B4A-F6F-öweiuj
ABC-DEF-17-021
AB-DEF-17-021
ABC-DEF-1
ABC-DEF
ABC-DEF-
';
preg_match_all($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