$re = '/(\S*(?:[Ss]mall|[Ll]arge|[Mm]edium|Med[.])\S*)/';
$str = 'some text Small some text"
2 "some text small-med some text"
3 "some text Med. some text"
4 "some text medium some text"
5 "some text med-large some text"
6 "some text large some text';
preg_match_all($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