// fonction qui construit l'objet httpRequest  
function ajax()
{
	var req = null; 
	if (window.XMLHttpRequest)   		//Firefox
	{
		req = new XMLHttpRequest();
		if (req.overrideMimeType) 
		{
			req.overrideMimeType('text/xml');
		}
	} 
	else if (window.ActiveXObject) 		//Internet Explorer
	{
		try {
			req = new ActiveXObject("Msxml2.XMLHTTP");
		} catch (e)
		{
			try {
				req = new ActiveXObject("Microsoft.XMLHTTP");
			} catch (e) {}
		}
	}
	return req;
}  

//affichage des sous-catégories
function show_subcat(id_cat)
{                                  
   req=ajax();
   req.open("GET", "show_subcat.php?id_cat="+id_cat, true); 
   req.send(null);
   
   req.onreadystatechange = function()  
   { 
      if(req.readyState == 4) 
   
      if(req.status == 200) 
      {
	     document.getElementById('div_subcat').innerHTML = req.responseText;
	    }	
      else	
      {
	     document.getElementById('div_subcat').innerHTML = "Error: returned status code " + req.status + " " + req.responseText;
      }	
    } 
  
}