我试图在另一个if语句中使用变量集，但它一直返回未定义。这是PHP代码:if(isset($_POST['bookingTime'])){$bookingTime=$_POST['bookingTime'];$bookingDate=$_POST['theDate'];$dbDateTime=$bookingDate."".$bookingTime;echojson_encode($dbDateTime);exit;}if(isset($_POST['bookingPwd'])){$pwd=$_POST['txtBookingPwd'];//Getthe$dbDateTimevaria