Serializing and submitting a form with jQuery and PHP

You can use this function

var datastring = $("#contactForm").serialize();
$.ajax({
    type: "POST",
    url: "your url.php",
    data: datastring,
    dataType: "json",
    success: function(data) {
        //var obj = jQuery.parseJSON(data); if the dataType is not specified as json uncomment this
        // do what ever you want with the server response
    },
    error: function() {
        alert('error handling here');
    }
});

return type is json

EDIT: I use event.preventDefault to prevent the browser getting submitted in such scenarios.

Adding more data to the answer.

dataType: "jsonp" if it is a cross-domain call.

beforeSend: // this is a pre-request call back function

complete: // a function to be called after the request ends.so code that has to be executed regardless of success or error can go here

async: // by default, all requests are sent asynchronously

cache: // by default true. If set to false, it will force requested pages not to be cached by the browser.

Find the official page here