PHP报错求助：Undefined index: password（register.php第91行）

Hey there, let's fix this error step by step! The Notice: Undefined index: password is a straightforward mismatch issue, and we'll also tackle some hidden problems in your code to make it more robust.

1. Core Cause of the Error #

Look at your SQL query: you're selecting the field user_password from the database, but on line 91, you're trying to access $results['password']. These two names don't match—there's no password key in your query results, hence the undefined index notice.

2. Step-by-Step Fixes #

Fix 1: Align Database Field Names #

Update the code to use the exact field name from your query:

• Change $results['password'] to $results['user_password'] (line 91)
• Also fix the session assignment line: $_SESSION['username'] = $results['username']; → $_SESSION['username'] = $results['user_name']; (since your query selects user_name, not username)

Fix 2: Correct Password Verification Logic #

Your current code uses hash('sha512',$password) then password_verify()—this is wrong. password_verify() only works with hashes generated by password_hash(), not raw SHA-512 hashes. Choose one of these options based on how you stored passwords:

• If your database uses password_hash() generated hashes: Remove the $hashpass = hash('sha512',$password); line, and verify directly with password_verify($password, $results['user_password'])
• If your database stores raw SHA-512 hashes: Skip password_verify() and compare hashes directly: $hashpass === $results['user_password']

Fix 3: Add Safe Parameter Retrieval (Recommended) #

To avoid similar undefined index issues from missing POST data, use null coalescing to set default values:

$username = trim($_POST['username'] ?? '');
$password = trim($_POST['password'] ?? '');

Corrected Code Snippet #

<?php 
session_start(); 

//DB configuration Constants 
define('_HOST_NAME_', 'localhost'); 
define('_USER_NAME_', 'user'); 
define('_DB_PASSWORD', ''); 
define('_DATABASE_NAME_', 'user'); 

//PDO Database Connection 
try { 
    $databaseConnection = new PDO('mysql:host=localhost; dbname=user; ', 'root', ''); 
    $databaseConnection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); 
} catch(PDOException $e) { 
    echo 'ERROR: ' . $e->getMessage(); 
} 

if(isset($_POST['login'])){ 
    $errMsg = ''; 
    // Safe parameter retrieval
    $username = trim($_POST['username'] ?? ''); 
    $password = trim($_POST['password'] ?? ''); 

    if($username == '') $errMsg .= 'You must enter your Username<br>'; 
    if($password == '') $errMsg .= 'You must enter your Password<br>'; 

    if($errMsg == ''){ 
        $records = $databaseConnection->prepare('SELECT user_id,user_name,user_password FROM user WHERE user_name = :username'); 
        $records->bindParam(':username', $username); 
        $records->execute(); 
        $results = $records->fetch(PDO::FETCH_ASSOC); 

        // Using password_verify for password_hash generated hashes
        if($results && password_verify($password, $results['user_password'])){ 
            $_SESSION['username'] = $results['user_name']; 
            header('location:index.php'); 
            exit; 
        }else{ 
            $errMsg .= 'Username and Password are not found<br>'; 
        } 
    } 
} 
?>

内容的提问来源于stack exchange，提问作者PeanutStick