function select_dossier(url) {
	var xhr_object = null;
	if(window.XMLHttpRequest) {
		// Firefox et autres navigateurs supportant le constructeur XMLHttpRequest()
		xhr_object = new XMLHttpRequest();
	} else if(window.ActiveXObject) {
		// Internet Explorer
		xhr_object = new ActiveXObject("Microsoft.XMLHTTP");
	} else { 
		// XMLHttpRequest non supporté par le navigateur
		alert("Votre navigateur ne supporte pas les objets XMLHTTPRequest...");
		return;
	}

xhr_object.onreadystatechange = function() {	
	if (xhr_object.readyState == 4) {
		var reponse=xhr_object.responseText;
document.getElementById("selection").innerHTML = reponse;

}
}

xhr_object.open("POST", url, true);
xhr_object.setRequestHeader('Content-Type','application/x-www-form-urlencoded');

num = document.getElementById('theme').value;
xhr_object.send("select="+num);
document.getElementById("affichage").innerHTML = '';	
document.getElementById("info").innerHTML = '';	
}
select_dossier("select_dossier.php");