function getXhr(){
	var xhr = null; 
	if(window.XMLHttpRequest) // Firefox et autres
		xhr = new XMLHttpRequest(); 
	else if(window.ActiveXObject){ // Internet Explorer 
		try {
			xhr = new ActiveXObject("Msxml2.XMLHTTP");
		} catch (e) {
			xhr = new ActiveXObject("Microsoft.XMLHTTP");
		}
	}
	else { // XMLHttpRequest non supporté par le navigateur 
		alert("Votre navigateur ne supporte pas les objets XMLHTTPRequest..."); 
		xhr = false; 
	} 
	return xhr;
}

function afficherPhoto(idCat){
	document.getElementById('loaderPhoto').innerHTML = '<img src ="../img/ajax-loader.gif"><br/>Chargement en cours...';
	document.getElementById('listeCommentaires').innerHTML = '';
			
	var xhr = getXhr();
	xhr.onreadystatechange = function(){
		if(xhr.readyState == 4 && xhr.status == 200){
			nouvellePhoto = xhr.responseText;
			document.getElementById('blocmiddle').innerHTML = nouvellePhoto;
		} 
	} 
	
	xhr.open("POST","include/ajax-photo.php",true);
	xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
		
	var data = "idCat="+idCat;  
	xhr.send(data); 
}