function createRequestObject() {
    var ro;
    var browser = navigator.appName;
    if(browser == "Microsoft Internet Explorer"){
        ro = new ActiveXObject("Microsoft.XMLHTTP");
    }else{
        ro = new XMLHttpRequest();
    }
    return ro;
}

var http = createRequestObject();
var show_loader;

function getSizes(obj)
{
		var pid = document.forms.product.pid.value;
		var chosen = obj.value;

		var url = "shop.php";
		var data = "action=getSizes&pid=" + pid + "&colour=" + chosen;
		http.open("POST", url, true);
		http.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
	    http.send(data);
		http.onreadystatechange = handleDrop;
		
		
}

function handleDrop() {
  if (http.readyState == 4) {
    if (http.responseText.indexOf('invalid') == -1) {
      qresults = http.responseText.split("-!-");
	  	  
		  var selbox = document.forms.product.option_size;
     	  selbox.options.length = 0;	   
			for (var i=0;i<qresults.length;i++)
			{
			
			split = qresults[i].split("---");
			if(split[0]) {
			  selbox.options[selbox.options.length] = new Option(split[0]+' ('+split[1]+')',split[0]);
			  }
			}

    }
  }
}