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

You can add extra data with form data

use serializeArray and add the additional data:

var data = $('#myForm').serializeArray();
    data.push({name: 'tienn2t', value: 'love'});
    $.ajax({
      type: "POST",
      url: "your url.php",
      data: data,
      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 handing here');
    }
});

 $("#contactForm").submit(function() {

    $.post(url, $.param($(this).serializeArray()), function(data) {

    });
 });