Метод POST с помощью JavaScript

<script>
    function createObject() {
            var request_type;
            var browser = navigator.appName;
            if(browser == "Microsoft Internet Explorer"){
                request_type = new ActiveXObject("Microsoft.XMLHTTP");
            } else {
                request_type = new XMLHttpRequest();
            }
            return request_type;
    }
    var http = createObject();

    function requestItem() {
            var post_str = '';
            var key_str;
            var val_str;
            for(var i=1; i < arguments.length; i++) {
                key_str=arguments[i];
                val_str = document.getElementById(arguments[i]).value;
                post_str +=key_str+'='+val_str+'&';
            }
            http.open("POST",arguments[0], true);
            http.onreadystatechange=echoPost;
            http.setRequestHeader("Content-type","application/x-www-form-urlencoded");
            http.send(post_str);
    }

    function echoPost()
    {
        if(http.readyState==4 && http.status==200)
        {
            var response = http.responseText;
            document.getElementById('cart').innerHTML = response;
        }
    }