Composer is PHP's package manager for installing and managing third-party libraries. Define dependencies in composer.json and run composer install. It also handles PSR-4 autoloading so you never need manual require statements.
Composer — PHP Dependency Manager
// Install Composer globally, then:
// composer init — create composer.json
// composer require vendor/package
// composer install — install all deps
// composer update — update deps
// composer dump-autoload — rebuild autoloader
// composer.json example
{
"require": {
"guzzlehttp/guzzle": "^7.0",
"vlucas/phpdotenv": "^5.0"
},
"autoload": {
"psr-4": { "App\\": "src/" }
}
}
// In your PHP file
require "vendor/autoload.php";
use GuzzleHttp\Client;
use App\Models\User; // src/Models/User.php (PSR-4)
$client = new Client();