PHP会话变量不跨页面传输

我有一个连接文件，它包含在我的文件头中。标题包含一个会话开始，我已经检查了会话ID在各个页面上是否相同。我试图在一些HTML中回显$_会话['userFirstName']，以显示用户名。我不明白为什么它是空白的。除了“注意：未定义索引：userFirstName”之外，Chrome没有其他错误消息

这是我的connect.php

<?php
/*Login handled here*/
$servername = "localhost";
$usernameDB = "root";
$passwordDB = "";
$nameDB = "teacheasy";

//set user and password to values from form
if ( isset($_POST['username']) && isset($_POST['password']) ) { 
    $user = $_POST['username'];
    $pass = $_POST['password'];
} else {
    echo "The values weren't sent";
}

//connect to the database
$_SESSION['connection'] = new mysqli($servername, $usernameDB, $passwordDB,$nameDB);

//Check if the connection was successful
if($_SESSION['connection']->connect_error){
    die("Connection to the database failed: " . $_SESSION['connection']->connect_error);
} else{
//once the DB is connected, get information from the DB to check the records against the data entered
    $sqlUser = "SELECT `teacher_username` FROM `teacher` WHERE `teacher_username`='$user'";
    $sqlPass = "SELECT `password` FROM `teacher` WHERE `password`='$pass'";
    $resultUser = mysqli_query($_SESSION['connection'], $sqlUser);
    $resultPass = mysqli_query($_SESSION['connection'], $sqlPass);
    $textUser = $resultUser->fetch_assoc();
    $textPass = $resultPass->fetch_assoc();

    //get first name and last name to populate the user
    $sqlUserFirstName = "SELECT `first_name` FROM `teacher` WHERE `teacher_username`='$user'";
    $sqlUserLastName = "SELECT `last_name` FROM `teacher` WHERE `teacher_username`='$user'";
    $resultUserFirstName = mysqli_query($_SESSION['connection'], $sqlUserFirstName);
    $resultUserLastName = mysqli_query($_SESSION['connection'], $sqlUserLastName);
    $_SESSION['userFirstName'] = $_POST[$resultUserFirstName->fetch_assoc()];
    $_SESSION['userLastName'] = $_POST[$resultUserLastName->fetch_assoc()];

    //check if the user and password match records in the database
    if($user == $textUser['teacher_username'] && $pass == $textPass['password']){
        //open the calendar if they match
        echo "<script> window.location.assign('../calendar.php'); </script>";
    } else{
        //set this up to load a log in failed page rather than a blank page with error message
        echo "The data entered has no match.";
    }

}

这就是你所做的

$user = $_POST['username']
// "SELECT `first_name` FROM `teacher` WHERE `teacher_username`='$user'" // SQL injection here
$_SESSION['userFirstName'] = $_POST[$resultUserFirstName->fetch_assoc()];

正如@jeroen在评论中所说，$\u SESSION['userFirstName']

必须为空，因为$\u POST中没有等于

$resultUserFirstName->fetch\u assoc（）

的键，它返回一个数组！。您应该会得到一个未定义的索引错误

$\u POST

是一个数组，用于保存已随http请求发布到服务器的变量。它与数据库查询返回的数据无关，除非

$\u POST['username']

=

教师。first\u name

和

教师。first\u name

=

教师。教师用户名

试一试

而不是

$_SESSION['userFirstName'] = $_POST[$resultUserFirstName->fetch_assoc()];

---

此外，您也容易受到攻击，因此您应该尽量始终使用准备好的语句。如果您习惯于连接，请检查此答案以了解如何进行连接。

我在其中没有看到任何链接。我也没有看到任何对标头的引用。顺便说一句，将DB连接放到会话中似乎是个坏主意。另一个a另一方面，为什么不使用

header

重定向而不是JS重定向？我很确定您不能使用数组作为数组键：

$\u SESSION['userFirstName']=$\u POST[$resultUserFirstName->fetch\u assoc（）]

。$\u POST变量您希望使用此变量得到什么？从@jeroen的观点出发，为什么您要执行两个查询而不是一个查询？请尝试使用准备好的语句。不必太苛刻，此代码到处都是，老实说，它很值得从头开始重写。一些教程也可能会很好地帮助您谢谢！我仍然没有想要的输出，我仍然有一个“注意：未定义的索引：userFirstName”错误这修复了我在connect中添加会话启动后的问题！

$_SESSION['userFirstName'] = $_POST[$resultUserFirstName->fetch_assoc()];