Mine

	this.postRequest= function( sender, params, callback)
	{
		var request= _XMLHttpRequest();
		request.onreadystatechange = callback;
		
		var requestString = "";
		params.sort();
		
		for(var i=0; i<params.length; i++)
		{
			requestString+=params[i];
			if(i!=params.length-1) requestString+="&";
		}

		//request.setRequestHeader('Content-Type', 'application/x-www-form urlencoded');		
		request.open("POST", this._serverUrl, true);
		request.send(requestString);
		
		return request;
	}