function sendRequest(url,params,HttpMethod) 
{ 
    // check if http method is defined, if not, set it to GET
    if(!HttpMethod) 
    {    
        HttpMethod="GET"; 
    } 
    
    // 
    // initialize request object 
    req=null; 
    if(window.XMLHttpRequest)
    {    
        req=new XMLHttpRequest; //mozilla/safari 
    } 
    else if(window.ActiveXObject)
    {    
        req=new ActiveXObject("Microsoft.XMLHTTP"); //internet explorer 
    } 
    // 
    //define callback handler 
    if(req) 
    { 
        //    
        req.onreadystatechange=onReadyState;    
        req.open(HttpMethod,url,true);    
        req.setRequestHeader("Content-Type","application/x-www-form-urlencoded");    
        req.send(params); 
    } 
} 

// 
function onReadyState() 
{ 
   var ready=req.readyState; 
   var data=null; 
   var quiz_question = document.getElementById("quiz_question");
   var questionnr    = document.getElementById("questionnr");
    
    if(ready==4)
    {   
		if (questionnr.value<16)
		{
			data=req.responseText; //read response data    
			//alert (data);
			quiz_question.innerHTML = data;
		}
		else
		{
			quiz_question.innerHTML = '<BR>';
		}
	}
}

function clicked_yes() 
{ 
	var questionnr      = document.getElementById("questionnr");
	var prevquestionnr  = parseFloat (document.getElementById("questionnr").value);
	var quiz_img        = document.getElementById("quiz_img");
	var quizsession     = document.getElementById("quizsession");
	var quiz		    = document.getElementById("quiztable");
    var quiz_question   = document.getElementById("quiz_question");
	
	//alert (prevquestionnr);
	if (questionnr.value>14)
	{
		questionnr.value = parseFloat (questionnr.value) + 1;
		sendRequest('/scripts/fetch_questions.php?question='+questionnr.value+'&prevquestion='+prevquestionnr+'&answer=Ja&quizid='+quizsession.value);   
		questionnr.value=0;
		quiz.innerHTML = '<TABLE cellpadding=0 cellspacing=0 border=0><TR><TD><IFRAME width=700 height=360 frameborder=0 SRC=scripts/display_quiz.php?quizid='+quizsession.value+'></TD></TR></TABLE>';
	}
	else
	{
		questionnr.value = parseFloat (questionnr.value) + 1;
		sendRequest('/scripts/fetch_questions.php?question='+questionnr.value+'&prevquestion='+prevquestionnr+'&answer=Ja&quizid='+quizsession.value);   
		quiz_img.src = 'images/vraag' + questionnr.value + '.jpg';
	}
}

function clicked_no() 
{ 
	var questionnr      = document.getElementById("questionnr");
	var prevquestionnr  = parseFloat (document.getElementById("questionnr").value);
	var quiz_img        = document.getElementById("quiz_img");
	var quizsession     = document.getElementById("quizsession");
	var quiz		    = document.getElementById("quiztable");
    var quiz_question   = document.getElementById("quiz_question");
	
	//alert (prevquestionnr);
	if (questionnr.value>14)
	{
		questionnr.value = parseFloat (questionnr.value) + 1;
		sendRequest('/scripts/fetch_questions.php?question='+questionnr.value+'&prevquestion='+prevquestionnr+'&answer=Nee&quizid='+quizsession.value);   
		questionnr.value=0;
		quiz.innerHTML = '<TABLE cellpadding=0 cellspacing=0 border=0><TR><TD><IFRAME width=700 height=360 frameborder=0 SRC=scripts/display_quiz.php?quizid='+quizsession.value+'></TD></TR></TABLE>';
	}
	else
	{
		questionnr.value = parseFloat (questionnr.value) + 1;
		sendRequest('/scripts/fetch_questions.php?question='+questionnr.value+'&prevquestion='+prevquestionnr+'&answer=Nee&quizid='+quizsession.value);   
		quiz_img.src = 'images/vraag' + questionnr.value + '.jpg';
	}
}