# Running PHP: CLI, Built-in Server, php.ini and Composer — PHP

Source: https://www.skillbyai.com/en/php/f-setup

> Run scripts from the command line and the built-in server, and start a Composer project.

## Tools you use every day

PHP runs in several **SAPIs** (server APIs): the **CLI** for scripts, workers and tests (`php script.php`); **PHP-FPM** (FastCGI Process Manager) behind NGINX or Apache in production; and the **built-in web server** (`php -S localhost:8000 -t public`) for local development only. Configuration lives in **`php.ini`**; `php --ini` shows which files are loaded and `php -m` lists extensions such as `pdo_pgsql`, `mbstring`, `intl` and `opcache`. In development, enable `display_errors` and `error_reporting = E_ALL`; in production, log errors instead of displaying them. **Composer** manages dependencies and autoloading: `composer init` creates `composer.json`, `composer require vendor/package` adds a dependency, `composer.lock` pins exact versions (commit it), and `vendor/autoload.php` loads classes automatically. Use **`composer install`** in deployments to install exactly what the lock file says, and `composer update` deliberately when you want newer versions. Docker images such as the official `php:8.x-fpm` are a common way to keep versions consistent across machines.

## A typical project start

Composer project, PSR-4 autoloading and the built-in server for development.

```bash
php -v                              # check the version
php -m | grep -i -E 'pdo|mbstring|intl|opcache'

mkdir shop && cd shop
composer init --name=acme/shop --type=project --no-interaction
composer require monolog/monolog
composer require --dev phpunit/phpunit phpstan/phpstan

# composer.json autoload section, then: composer dump-autoload
# "autoload": { "psr-4": { "Shop\\": "src/" } }

php -S localhost:8000 -t public     # development server only, never production
```

## A kitchen with a pantry list

`composer.json` is your shopping list ("some flour, version 2 or newer"); `composer.lock` is the receipt saying exactly which brand and pack you bought. Every cook who uses the receipt ends up with identical ingredients.

**Quiz:** Why should composer.lock be committed to version control for applications?

- [ ] It contains your source code
- [ ] Composer cannot run without Git
- [ ] It stores database passwords
- [x] It pins exact dependency versions so every environment installs the same packages

*Answer:* It pins exact dependency versions so every environment installs the same packages. The lock file makes installs reproducible across developers, CI and production.