$re = '/\([\w\s]*\(*[\w\s]*[()]*[\w\s]*\)\)/';
$str = 'Example(123) (Example (123))
Hello World (Hello World (123))
any_string_abc (anything) (any_string (whatever)(whatever123))';
preg_match_all($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