$re = '/(?:MP)([0-9]{1,}|[0-9]{1,}\.|\.[0-9]{1,}|[0-9]{1,}\.[0-9]{1,}|)(?:\s{1,})(.{1,})/';
$str = 'MP1 Chicago
MP7 Chicago
MP1. Chicago
MP7. Chicago
MP.1 Chicago
MP.7 Chicago
MP1.1 Chicago
MP7.7 Chicago
MP1Chicago
MP7Chicago
MP1.Chicago
MP7.Chicago
MP.1Chicago
MP.7Chicago
MP1.1Chicago
MP7.7Chicago';
preg_match_all($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