What is CodeIgniter 4 Shield (authentication package)?
Why Interviewers Ask This
Interviewers ask this to evaluate whether you have the depth of knowledge needed to mentor others and lead technical decisions. The expected answer goes beyond definitions into practical implications and real-world consequences.
Answer
CodeIgniter Shield is the official first-party authentication and authorization package for CI4. Install: composer require codeigniter4/shield. Setup: php spark shield:setup — creates authentication tables, config files, and optionally adds routes. Features: user registration and login (email/password, username/password), session-based auth for web, token-based auth for APIs (similar to Sanctum), magic link login (passwordless email links), two-factor authentication, remember me, email verification, and authorization (groups and permissions). Protect routes: $routes->group("", ["filter" => "session"], function($routes) { ... }). Get current user: auth()->user(). Check permission: auth()->user()->can("read posts"). Shield is the recommended alternative to rolling your own auth in CI4 apps.
Pro Tip
Before answering, structure your response: one-line definition → real-world analogy → concrete example from a project. This makes even complex CodeIgniter answers easy to follow.
Previous
What is CodeIgniter 4's multiple database support?
Next
What is CodeIgniter 4 named routes and URL generation?