$re = '/(?<identifier>[a-zA-Z][a-zA-Z0-9_]*)(?<specifier>[%&@!#$])?(?:\sAs)?\s(?:(?<reference>[a-zA-Z][a-zA-Z0-9_]*)\s)?=\s(?<value>[^\',]+(?:(?:(?!").)+")?),?/';
$str = 'foo = "123,"
foo = 123,
foo = "123"
';
preg_match_all($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