var postRequest = false;
   
   function makePOSTRequest(url, parameters,func) {
      postRequest = false;
      if (window.XMLHttpRequest) { //dit object is beschikbaar in ff, safari, ie7+ etc.
         postRequest = new XMLHttpRequest();
         if (postRequest.overrideMimeType) { //
            postRequest.overrideMimeType('text/html');
         }
      } else if (window.ActiveXObject) { //dit object is beschikbaar in ie5.5+
         try {
            postRequest = new ActiveXObject("Msxml2.XMLHTTP"); //ie 6+
         } catch (e) {
            try {
               postRequest = new ActiveXObject("Microsoft.XMLHTTP"); //ie 5.5
            } catch (e) {}
         }
      }
      if (!postRequest) {
         alert('Cannot create XMLHTTP instance');
         return false;
      }
      postRequest.onreadystatechange = func;
      postRequest.open('POST', url, true);
      postRequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
      postRequest.setRequestHeader("Content-length", parameters.length);
      postRequest.setRequestHeader("Connection", "close");
      postRequest.send(parameters);
   }

function getSubcats(cat) {
	var poststr = "cat="+cat;
	if(cat) {
		makePOSTRequest('php/ajax_getSubcats.php', poststr, updateSubcats);
	}
}

function updateSubcats() {
	if (postRequest.readyState == 4)  {
		if (postRequest.status == 200) { //checken of de aanvraag ok is.
			var subcat = document.getElementById('zoek_subcat');
			var stringSubcats = postRequest.responseText;
			stringSubcats = stringSubcats.substr(1);
			if(!stringSubcats.length) {
				subcat.innerHTML = '<select name="subcat" disabled><option value="">Geen categorie beschikbaar</option></select>';
			} else {
				var subcats = stringSubcats.split(',');
				var totalString = '<select name="subcat">';
				totalString += '<option value="">Alle categorieën</option>';
				for(i=0;i<subcats.length;i++) {
					totalString += '<option value="'+subcats[i]+'">'+ucfirst(subcats[i])+'</option>';
				}
				totalString += '</select>';
				subcat.innerHTML = totalString;
			}
		}
	}
}

function ucfirst (str) {
    // http://kevin.vanzonneveld.net
    // +   original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   bugfixed by: Onno Marsman
    // +   improved by: Brett Zamir (http://brett-zamir.me)
    // *     example 1: ucfirst('kevin van zonneveld');
    // *     returns 1: 'Kevin van zonneveld'
 
    str += '';
    var f = str.charAt(0).toUpperCase();
    return f + str.substr(1);
}