How jsonp works, detailed explanation plz refer to http://www.onlinesolutionsdevelopment.com/blog/web-development/javascript/jsonp-example/

jsonp.js

<script type="text/javascript">// <![CDATA[
    function callTheJsonp()
    {
        // the url of the script where we send the asynchronous call
        var url = "http://localhost/utils/jsonp/ajax.php?callback=parseRequest";
        // create a new script element
        var script = document.createElement('script');
        // set the src attribute to that url
        script.setAttribute('src', url);
        // insert the script in out page
        document.getElementsByTagName('head')[0].appendChild(script);
    }
 
    // this function should parse responses.. you can do anything you need..
    // you can make it general so it would parse all the responses the page receives based on a response field
    function parseRequest(response)
    {
        try // try to output this to the javascript console
        {
            console.log(response);
        }
        catch(an_exception) // alert for the users that don't have a javascript console
        {
            alert('product id ' + response.item_id + ': quantity = ' + response.quantity + ' & price = ' + response.price);
        }
    }
 
// ]]></script>

<span onclick="callTheJsonp()">click here to make the jsonp call</span>