$re = '/([a-z]+)((?:,\s*[a-z]+)*)\s+(and|or)\s+([a-z]+)/';
$str = 'white and blue ... white, and blue ... dark, green, gray and silver';
preg_match_all($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