//get XHR object
function getXHR(){
	if(window.XMLHttpRequest){
		http_request = new XMLHttpRequest();
		if(http_request.overrideMimeType)
			http_request.overrideMimeType("text/xml");
	}
	else if(window.ActiveXObject){
		http_request = new ActiveXObject("Microsoft.XMLHTTP");
	}
	if(!http_request){
		alert("页面异常");
		return false;
	}
}
function sendRequest(url){
	getXHR();
	http_request.onreadystatechange = processRequest;
	http_request.open('GET',url,true);
	http_request.send(null);
}
function sendRequestSecond(url){
	getXHR();
	http_request.onreadystatechange = callSumPlan;
	http_request.open('GET',url,true);
	http_request.send(null);
}