PHP with Laravel

Default: the current PHP 8.x, Laravel (the mainstream framework — choose a micro-framework only with a written reason, "it is lighter" is not one), MySQL 8 or SQLite for tests, Composer, PHPUnit or Pest, Docker Compose to run everything.

Setup

1. composer create-project laravel/laravel app inside a PHP container, so the host needs only Docker.
2. Keep local settings in the environment file Laravel reads at start-up, commit only the example file without secrets, and generate APP_KEY per environment.
3. Compose services: app (php-fpm or php artisan serve for development), db (MySQL with a named volume), optional queue.

Modelling

• One migration per schema change; never edit a migration that has run anywhere else — add a new one.
• Use Eloquent casts for types ('price' => 'integer', 'bought_at' => 'immutable_datetime').
• Store money in integer minor units and quantities with explicit units (grams, millilitres). Convert at the edge.
• Validate input with Form Requests; keep controllers thin and put calculations in plain service classes you can unit-test.

Calculations people check by hand

For price-per-unit, discounts and point rebates:

• Compute in integers or bcmath; floats produce off-by-one-yen style errors.
• Write down the rounding rule (floor, round half up, banker's) and test the boundary cases.
• Keep the history of inputs so a result can be explained later ("previous price", "change since last time").

Testing

• php artisan test with an in-memory SQLite database (DB_CONNECTION=sqlite, DB_DATABASE=:memory:) for speed, plus a CI job against MySQL if you use MySQL-specific features.
• Use factories for test data and RefreshDatabase to isolate tests.
• Feature tests over HTTP for routes, unit tests for services.

Verification loop

1. composer validate and php -l on changed files.
2. vendor/bin/pint --test (formatting) and a static analyser (Larastan/PHPStan) at a level you keep green.
3. php artisan test.
4. docker compose up from a clean checkout to prove the setup instructions work.

Pitfalls

• Mass assignment: define $fillable (or $guarded) on every model.
• N+1 queries: eager-load relations with with(); enable Model::preventLazyLoading() in development.
• Time zones: set APP_TIMEZONE and store UTC in the database; MySQL TIMESTAMP converts, DATETIME does not.
• Strict mode in MySQL rejects invalid dates and truncation that older setups accepted; keep it on and fix the data.
• Config cache: after php artisan config:cache, env() outside config files returns null. Read settings through config().
• Composer platform: set config.platform.php to the production PHP version so dependency resolution matches.