I am getting ajax response in array format from php url. How to extract array response values in jQuery? FYI:

PHP dizidir:

$response = array('msg' => 'Hello', 'html' => '<b>Good bye</b>');

Benim ajax cevaben $ yanıtı dizi alıyorum. yani

var promo = "promo=45fdf4684sfd";
$.ajax({
    type: "POST",
    url: baseJsUrl + "/users/calc_discount",
    data: promo,
    success: function (msg) { // I am getting $response here as ajax response.
        //alert(msg);

        // Here I want to check whether response is in array format or not. if it is in array format, I want to extract msg here and want to use response array values.
    }
});

Let me know answer pls. Thanks.