Authentication · Lesson 2 of 7

Login System

Verify submitted credentials and establish a fresh authenticated session.

Lesson

Login looks up the account and verifies the submitted password against its stored hash with password_verify. Use a generic failure message, rate-limit attempts, and regenerate the session ID after success. Never compare plaintext passwords or reveal account existence through different errors. Authentication confirms identity; each protected action still needs authorization. Further guidance Use PHP password hashing APIs, regenerate a session identifier after authentication, and clear session state during logout. Authentication identifies the user; authorization checks whether that user may perform this action on this record. Rate-limit sensitive endpoints and keep failure messages generic. Practice task: Create a fresh example for Login System. Predict the result before running it, then change one input and explain why the result changes. Test a normal case and one boundary or invalid case where it applies. Compare your output with the example and note one rule you would use in a real project.

Code examples

PHP

if ($user && password_verify($password, $user['password'])) {
    session_regenerate_id(true);
    $_SESSION['user_id'] = $user['id'];
}

Expected output

A new authenticated session after valid credentials

Key points

Verify submitted credentials and establish a fresh authenticated session.
Store password hashes, not plaintext passwords.
Check authorization on every protected operation.

Your learning progress

Finish this lesson

Optional practice

PHP playground

This site does not execute learner-provided PHP code. Connect a secured PHP sandbox service before enabling code execution.

Execution is disabled. No code is sent to a server.