$re = '/=\s*((?:[^,"]|"\s*([^"]*?)\s?")+?)(?=\s*,|$)/';
$str = 'Digest realm = "http-auth@example.org",
qop= " auth, auth-int ", algorithm = MD5 ,
nonce ="7ypf/xlj9XXwfDPEoM4URrv/xwf94BcCAzFZH4GiTo0v" ,
opaque="FQhe/qaU925kfnzjCev0ciny7QMkPqMAFRtzCUYo5tdS"';
preg_match_all($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