$re = '/%[A-Za-z0-9]+%[!\.,]?/';
$str = '%test%
%another%!
%XxXDumbUserName420XxX%
%yo.%
%yo%.
%not a match%
%also.not%
42%';
preg_match_all($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