欢迎页取数据库数据遇错误：尝试访问null类型值的数组偏移量

Hey there, let's figure out why you're hitting that error! The notice means your $row variable is null when you try to access $row['nume'] on line 10—this happens when your database query doesn't return any matching user data. Here's how to diagnose and fix this step by step:

1. Make sure your session is set up correctly #

First, move session_start() to the very top of your file (before including any other files) to avoid issues with headers already being sent. Also, always validate that $_SESSION['login_user'] exists and has a value before using it in a query:

<?php
session_start(); // Move this to the top

// Check if the session variable exists and isn't empty
if(!isset($_SESSION['login_user']) || empty($_SESSION['login_user'])){
    header("location:login.php");
    die();
}

include('config.php');
$user_check = $_SESSION['login_user'];

2. Fix your database query (and avoid SQL injection!) #

Your current query directly inserts the session value into SQL, which is a huge security risk (SQL injection) and can break the query if the username has special characters (like a single quote). Use prepared statements instead, and add error handling to catch query issues:

// Replace your old query with this prepared statement
$stmt = mysqli_prepare($db, "SELECT nume FROM users WHERE nume = ?");
mysqli_stmt_bind_param($stmt, "s", $user_check);
mysqli_stmt_execute($stmt);
$result = mysqli_stmt_get_result($stmt);

// Check if the query ran successfully
if(!$result){
    die("Query failed: " . mysqli_error($db));
}

3. Handle cases where no user is found #

Even if the query runs, there might be no user matching the session value. Always check if $row is not null before accessing its values:

$row = mysqli_fetch_assoc($result);
if(!$row){
    // No user found—redirect to login
    header("location:login.php");
    die();
}

$login_session = $row['nume'];

Full corrected code #

Putting it all together, your session.php should look like this:

<?php
session_start();

if(!isset($_SESSION['login_user']) || empty($_SESSION['login_user'])){
    header("location:login.php");
    die();
}

include('config.php');
$user_check = $_SESSION['login_user'];

$stmt = mysqli_prepare($db, "SELECT nume FROM users WHERE nume = ?");
mysqli_stmt_bind_param($stmt, "s", $user_check);
mysqli_stmt_execute($stmt);
$result = mysqli_stmt_get_result($stmt);

if(!$result){
    die("Query failed: " . mysqli_error($db));
}

$row = mysqli_fetch_assoc($result);
if(!$row){
    header("location:login.php");
    die();
}

$login_session = $row['nume'];
?>

This fixes the null error, makes your code more secure, and adds safeguards to handle edge cases where the session or user data is missing.

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