$re = '/(?<=\(|,)\s*(.*?)\s*(?=\)|,)/m';
$str = 'List(UT_LVL_17_CD, UT_LVL_20_CD, 2018 1Q, 2018 2Q, 2018 3Q, 2018 4Q, 2018 FY )';
preg_match_all($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