php微信支付回调验证

       //字典排序拼接字符串
	function getWxPaySignature($arr){
	    ksort($arr);
	    $str = '';
	    foreach ($arr as $k=>$v){
	        if($k != "sign" && $v != "" && !is_array($v)){
                $str .= $k . "=" . $v . "&";
            }
	    }
	    $str = trim($str,'&');
	    return $str;
	}
	//微信回调验证
	function weCallbackCheck($xml){
	    $signArr = (array)$xml;
	    $sign = $signArr['sign'];
	    $stringA = getWxPaySignature($signArr);//数组字典排序拼接字符串
	    $stringSignTemp = $stringA.'&key=xxx';//设置的key
	    $signValue = md5($stringSignTemp);
	    $signValue = strtoupper($signValue);
	    if($signValue == $sign){
	        return 'success';//支付成功
	    }else{
	        return 'failure';
	    }
	}

        //使用方法
        $xmlstr = file_get_contents("php://input");
		$xml=simplexml_load_string($xmlstr, 'SimpleXMLElement', LIBXML_NOCDATA);
		if(weCallbackCheck($xml)=="success"){
                      //todo
                }