function getXhr(){
	var xhr = null;
	
	if(window.XMLHttpRequest){
		xhr = new XMLHttpRequest();
	}
	else if(window.ActiveXObject){
		try{
			xhr = new ActiveXObject("Msxml2.XMLHTTP");
		}
		catch(e){
			xhr = new ActiveXObject("Microsoft.XMLHTTP");
		}
	}
	else{
		alert('Veuillez mettre votre navigateur à jour !');
		xhr = false;
	}
	
	return xhr;
}

function envoyerRequete(url, post, xml, fct){
	var xhr = getXhr();
	
	xhr.onreadystatechange = function(){
		if(xhr.readyState == 4 && xhr.status == 200){
			if(fct){
				if(xml) fct(xhr.responseXML);
				else fct(xhr.responseText);
			}
		}
	}
	
	var postRequest = (post != null);
	xhr.open(postRequest ? "POST" : "GET", url, true);
	if(postRequest) xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
	xhr.send(post);
}