php - 我正在尝试使用 post 方法将变量从 PHP 传递到 HTML，但它对我不起作用

Question

这是我的PHP代码页

 <?php

    session_start();

    //include database connection
    include_once("dbconn.php");
    //afetr click the submit button the below code will be impelemnted  
    if(isset($_POST['id'])){

    $id=$_POST['id'];
    $Type=$_POST['Type'];
    $Avalibility=$_POST['Avalibility'];

    # insert data into MySQL database

    $sql1 =" update $Type set Reserve=1 where APP_ID=$id ";

    $sql2="INSERT INTO appointment_summary 
    SELECT Fname,Dep_Name,".$_SESSION['login_user'] .",D_ID,Hospital_Name,Hospital_Type,'".$_SESSION['Reason']."',APP_ID,Avalibility
    FROM $Type
    where APP_ID=$id";

    $sql3="select * from appointment_summary  where P_ID=".$_SESSION['login_user'] ." and Availability ='$Avalibility' ";

        $result=$conn->query($sql3);

        if ($result->num_rows != 1) {
              $conn->query($sql2);
             $conn->query($sql1);


                      echo "<script>
    alert('Your appointment has been succssfuly add');
    window.location.href='CheckAppoinmnets.php';
    </script>";



         } else {
             $Invalid="<p style=\"color:red;\"> You alrredy have an appointment in this time</p>";
             $_SESSION['Invalid']=$Invalid;  
    }


    }

    //enter code here

    $conn->close();

我在 HTML 页面中使用的这段代码

       <?php 
               if(isset($_POST['id'])){
              echo  $_SESSION['Invalid'];
               } 
              ?>

Answer 1

试试下面的代码

<?php 
  session_start();        
  if(isset($_REQUEST['id'])){
    echo  isset($_SESSION['Invalid'])?$_SESSION['Invalid']:'';
  } 
?>

如果你在 ID 和 SESSION 中都有值，它应该打印