$_SESSION 和所有 $_POST 部分的未定义索引答案

【问题标题】：undefined index on $_SESSION and all $_POST part$_SESSION 和所有 $_POST 部分的未定义索引
【发布时间】：2017-05-06 01:06:18
【问题描述】：

我想为我的网站制作注册表。但我遇到了错误，这是我的代码：

<?php

/* Registration process, inserts user info into the database 
and sends account confirmation email message
*/

// Set session variables to be used on profile.php page

$_SESSION['email'] = $_POST['email'];
$_SESSION['first_name'] = $_POST['firstname'];
$_SESSION['last_name'] = $_POST['lastname'];


$mysqli = mysqli_connect("localhost","root","","data");

// Check connection
if (mysqli_connect_errno())
 {
 echo "Failed to connect to MySQL: " . mysqli_connect_error();
 }

 // Escape all $_POST variables to protect against SQL injections
$first_name = $mysqli->escape_string($_POST['firstname']);
$last_name = $mysqli->escape_string($_POST['lastname']);
$email = $mysqli->escape_string($_POST['email']);
$password = $mysqli->escape_string(password_hash($_POST['password'],                     
PASSWORD_BCRYPT));
 $hash = $mysqli->escape_string( md5( rand(0,1000) ) );

  // Check if user with that email already exists
  $result = $mysqli->query("SELECT * FROM login WHERE email='$email'") or        
 die($mysqli->error());

// We know user email exists if the rows returned are more than 0
if ( $result->num_rows > 0 ) {

$_SESSION['message'] = 'User with this email already exists!';
header("location: error.php");

  }
 else { // Email doesn't already exist in a database, proceed...

// active is 0 by DEFAULT (no need to include it here)
$sql = "INSERT INTO login (first_name, last_name, email, password, hash)" 
        ."VALUES ('$first_name','$last_name','$email','$password',     '           
   $hash')";

// Add user to the database
if ( $mysqli->query($sql) ){

    $_SESSION['active'] = 0; //0 until user activates their account with    

  verify.php
    $_SESSION['logged_in'] = true; // So we know the user has logged in
    $_SESSION['message'] =

             "Confirmation link has been sent to $email, please verify
             your account by clicking on the link in the message!";

    // Send registration confirmation link (verify.php)
    $to      = $email;
    $subject = 'Account Verification ( clevertechie.com )';
    $message_body = '
    Hello '.$first_name.',

    Thank you for signing up!

    Please click this link to activate your account:

    http://localhost/login-system/verify.php?email='.$email.'&               
    hash='.$hash;  

    mail( $to, $subject, $message_body );

    header("location: profile.php"); 

     }


else {
    $_SESSION['message'] = 'Registration failed!';
    header("location: error.php");
    exit();
}

 }

错误状态：

Undefined index: firstname, lastname, email, password

在行设置会话变量和转义所有 $_POST 变量以保护 SQL 注入的行。任何人都知道如何解决此错误。谢谢。

【问题讨论】：

标签： php mysqli registration

【解决方案1】：

您在代码开头缺少session_start()，需要在您向浏览器回显/输出任何内容之前调用它。

您还需要将 session_start 添加到您的 error.php 以从那里读取会话。

当 session_start() 被调用或会话自动启动时，PHP 将调用打开和读取会话保存处理程序...

读取回调将检索任何现有的会话数据（以特殊的序列化格式存储）并将被反序列化并用于在读取回调将保存的会话数据返回给 PHP 会话处理时自动填充 $_SESSION 超全局变量。

见：http://php.net/manual/en/function.session-start.php

【讨论】：

【解决方案2】：

If(isset($_POST['first_name']) &&     isset($_POST['last_name']) && isset($_POST['email'])){
 // Escape all $_POST variables to protect  against SQL injections
$first_name = $mysqli->escape_string($_POST['firstname']);
$last_name = $mysqli- >escape_string($_POST['lastname']);
}

在 PHP 中，从未设置过的变量或数组元素不同于值为 null 的变量或数组元素；试图访问这样一个未设置的值是一个运行时错误。

这就是您遇到的问题：数组 $_POST 在索引“用户名”处没有任何元素，因此解释器会在您的程序进入无效测试之前中止您的程序。

【讨论】：