Namespaces, Composer & Autoloading

What you'll walk away with

Explain the PHP runtime and web behavior behind Namespaces, Composer & Autoloading
Test normal, boundary, invalid, and failure cases
Write secure and maintainable PHP

Composer resolves locked dependencies and maps namespaces to source directories.

Build a Complete Mental Model

Namespaces separate code names, while Composer provides dependency resolution, a lockfile, and PSR-4 autoloading. Commit `composer.lock` for applications and use deterministic installs in production.

Apply It in Real PHP

Run and test an original Namespaces, Composer & Autoloading example with normal, boundary, invalid, and failure inputs, recording output, warnings, exceptions, and side effects.

After This Lesson

Explain the contract and security boundary of Namespaces, Composer & Autoloading
Run an original working example
Automate an invalid or failure case

json

{
  "require": { "php": "^8.4 || ^8.5" },
  "autoload": { "psr-4": { "App\\": "src/" } }
}

You should see

Composer generates vendor/autoload.php

Try It Yourself

Run and test an original Namespaces, Composer & Autoloading example with normal, boundary, invalid, and failure inputs, recording output, warnings, exceptions, and side effects.

Security and Common Mistake

Running `composer update` in production can change dependency versions unexpectedly.

Composer Basic Usage and Autoloading — Composer

Easy traps

Running `composer update` in production can change dependency versions unexpectedly.
Assuming one sample output proves input, output, authorization, and every failure path are correct.

Hands-on Exercise

Run and test an original Namespaces, Composer & Autoloading example with normal, boundary, invalid, and failure inputs, recording output, warnings, exceptions, and side effects.

You'll know it worked when: App classes autoload from src/.