dongpo2458 2014-01-15 12:06
浏览 299
已采纳

尝试读取$ _SESSION数组时“注意:未定义的索引”[重复]

I have an irritating problem and I can't seem to fix it, I watched some videos on YouTube and read through the php.net documentation about error but this $_SESSION error needs your help!

The exact error, I get is this:

Notice: Undefined index: previouspage
C:\Users\Administrator\Documents\Localhostoot\test\index.php on line 5

What I have created is a goback button using a session variable. When the variable is already defined in my script there's no problem but when "the user" visits the website for the first time there is no "previous page" yet. The error above is what I then get. How can I fix this?

I have this PHP code:

<?php 

session_start();

if($_SESSION["previouspage"]) {
    echo "<a href=".$_SESSION["previouspage"].">Go back.</a>";
    $_SESSION["previouspage"] = "index.php";
}else {
    //No go back button will be displayed.
    $_SESSION["previouspage"] = "index.php";
}

?>

So, when there's no history yet I get the error, otherwise not. How to fix this?

</div>
  • 写回答

3条回答 默认 最新

  • doulianglou0898 2014-01-15 12:09
    关注

    Use isset() function:

    if(isset($_SESSION["previouspage"])) {
       echo "<a href=".$_SESSION["previouspage"].">Go back.</a>";
       $_SESSION["previouspage"] = "index.php";
    }else {
        //No go back button will be displayed.
        $_SESSION["previouspage"] = "index.php";
    }
    
    本回答被题主选为最佳回答 , 对您是否有帮助呢?
    评论
查看更多回答(2条)

报告相同问题?

悬赏问题

  • ¥15 3DTiles数据转换
  • ¥15 c++代码数据结构理解含义
  • ¥15 anaconda相关启动程序问题
  • ¥15 关于#hyperledger#的问题,如何解决?
  • ¥30 使用opencv中的solvePnPRansac计算相机位姿后,误差较大
  • ¥15 串口控制LED灯驱动板设计
  • ¥15 如何在unity场景里做到通过按钮实现模型替换
  • ¥15 uniapp的websocket和c++的websocket服务器通讯 发送的数据和接受的数据表现形式不一样
  • ¥15 pyspark配置中的错误
  • ¥15 html word表格