function ajax()
{
    var xhr=null;
    var game=document.getElementById('game_select').value;
	var tmp=document.getElementById('tps').value;
	var slot_game=document.getElementById('slot_game').value;
	var slot_voice=document.getElementById('slot_voice').value;
	var voice=document.getElementById('voice').value;
	if(document.forms["commande"].pro.checked)
	{
		var opt= 1;
	}
	else
	{
		var opt= 0;
	}
    if (window.XMLHttpRequest) { 
        xhr = new XMLHttpRequest();
    }
    else if (window.ActiveXObject) 
    {
        xhr = new ActiveXObject("Microsoft.XMLHTTP");
    }
    xhr.onreadystatechange = function() { alert_ajax(xhr,tmp,slot_game,slot_voice); };    
    xhr.open("GET", "js/php/tarif.php?game="+game+"&opt="+opt+"&voice="+voice, true);
    xhr.send(null);
	
}

function alert_ajax(xhr,tmp,slot_game,slot_voice)
{
    if (xhr.readyState==4) 
    {
    	var docXML= xhr.responseXML;
    	var game = docXML.getElementsByTagName("game");
		var voice = docXML.getElementsByTagName("voice");
		var prix_game = game.item(0).firstChild.data * slot_game;
		var prix_voice= voice.item(0).firstChild.data * slot_voice;
		var prix_total= prix_game+prix_voice;
    	document.getElementById("txt").value= prix_total * tmp+" € TTC";
    }
}