$re = '/\w+\s\d+[^\()](?=[()]*$)|\w+\s\w+\s\d+[^\()](?=[()]*$)/m';
$str = '(ABC 123) Text string (DEF 456)
(ABC 123) Text string (DEF 456)
(ABC 123) Text string (DEFG 123)
(ABC 123) Text string (ABC DEF 123)
Text string (ABC 123) (DEF 456)
(ABC 123) Text string (DEFG 123) (DEFG 123)
(ABC 123) Text string (123)';
preg_match_all($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