Question

我正在尝试通过下拉onchange事件更新会话值，并将此会话值用于第二页。为此，我添加了以下下拉列表和一个提交按钮。按下提交按钮我正在更新会话值。它正在工作，但大多数情况下，即使在更改下拉列表选项后它也会提供上一个会话值。它是错误的

<?php
     session_start(); // start session before output
     if( isset($_POST['submit']) ) { // some other page is posting to this page?
          // save values from other page to session
        $_SESSION['amount'] = $_POST['select_amount']; 

     }
?>


<form name="myForm"  action="/thanks" method="POST">

<table> <tr> <td style="width:272px;">
<select name="select_amount" id="select_amount" onchange="submit()">
  <option value="0">select a listing type</option>
  <option value="10">Premium Listings </option>
  <option value="20">Premium Blogs </option>
  <option value="30">1 week sticky </option>
</select></td>

 <td style="text-align:left;color:gray;"><span style="color:crimson;">*
 </span>Select a listing type</td></tr> </table>
 <table> <tr> 

<input type="submit" name="submit" class="button_add" onsubmit="return 
validateForm()">

</form>

Answer 1

如果您想使用on change更改会话值，则无需表单提交，使用ajax然后您可以轻松完成

Step1 ：像这样创建你的主文件

<?php
session_start(); // for show your session value 
print_r($_SESSION); // remove this after check
?>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<form name="myForm" action="/thanks" method="POST">

    <table>
        <tr>
            <td style="width:272px;">
                <select name="select_amount" id="select_amount" onchange="update_session_value(this.value)">
                    <option value="0">select a listing type</option>
                    <option value="10">Premium Listings</option>
                    <option value="20">Premium Blogs</option>
                    <option value="30">1 week sticky</option>
                </select></td>

            <td style="text-align:left;color:gray;">
                <span style="color:crimson;">*
            </span>Select a listing type
            </td>
        </tr>
    </table>
    <input type="submit" name="submit" class="button_add" onsubmit="return validateForm()">

</form>

<script>
    function update_session_value(value) {
        $.ajax({
            type: "POST",
            url: 'http://localhost/session.php', // change url as your 
            data: 'select_amount=' + value,
            dataType: 'json',
            success: function (data) {

            }
        });
    }

</script>

然后创建简单的session.php文件

<?php
session_start();
if( isset($_POST['select_amount']) ) {
    // save values from other page to session
    $_SESSION['amount'] = $_POST['select_amount'];

}
?>

更改后刷新页面，您可以看到此结果

Answer 2

对变更事件使用ajax调用

$("#select_amount").change(function(){
var select_amount = $("#select_amount option:selected").val();
        $.post('change_session.php',{select_amount : 'store'},function(data){
            if(data != ''){
                alert(data);
            }
        });
});

将PHP脚本放在

上

change_session.php

如何在下拉列表更改时更新会话变量？

2 个答案: