devsetup1-7  Exercise 2: A Composer Project
============================================

STEPS
-----
    sudo apt install composer git unzip       # if not already installed
    composer --version

    mkdir -p ~/projects/composer-demo && cd ~/projects/composer-demo
    composer init --no-interaction --name="me/composer-demo"
    composer require monolog/monolog
    ls
    # composer.json  composer.lock  vendor

Create app.php:

    <?php
    require __DIR__ . '/vendor/autoload.php';

    use Monolog\Logger;
    use Monolog\Handler\StreamHandler;

    $log = new Logger('demo');
    $log->pushHandler(new StreamHandler('php://stdout'));
    $log->info('Hello from Composer on ' . gethostname());

Run it:

    php app.php
    # a log line such as: [2026-09-30T12:00:00.000000+00:00] demo.INFO: Hello from Composer on devserver [] []

Now prove vendor/ is disposable:

    rm -rf vendor
    php app.php               # fails: Failed opening required 'vendor/autoload.php'
    composer install
    php app.php               # works again

Add a .gitignore containing:

    vendor/

INSTALL VS UPDATE
-----------------
composer install
  Reads composer.lock and installs EXACTLY the versions recorded there. If
  there is no lock file it resolves versions and creates one. The result is
  the same on every machine, which makes it the right command for rebuilding a
  project or deploying it.

composer update
  Ignores the lock file, fetches the newest versions that composer.json
  allows, installs them, and REWRITES composer.lock. Use it when you
  deliberately want to upgrade, then test, then commit the new lock file.

WHAT TO COMMIT
--------------
Commit: composer.json, composer.lock, your own code, and .gitignore.
Do not commit: vendor/. It is large, it is rebuilt from the lock file, and
committing it makes the history noisy.

WHY THIS WORKS AS AN ANSWER
---------------------------
Deleting vendor/ and getting it back shows that the lock file, not the
folder, is the record of the project's dependencies. The install/update
distinction is the same one as npm ci and npm install in Chapter 6.