$re = '/^(VI[0-9]{4}(?:BV)?(?:\d{2})?(D|H|MIN|MAX)?)+$/m';
$str = '6789
VI2111
VI2122
VI2122MIN
VI2122MAX
VI2122MUN
VI210021
VI210021D
VI210021H
VI210021X
VI2100BVMIN
VI2100BVMAX
VI2100
VI21001';
preg_match_all($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