It's an amazing tool. Simplifies dependencies management for PHP projects. After really simple installation or setup you just define dependencies in JSON format in composer.json file like this.. { "repositories": [ { "type": "pear", "url": "pear.php.net" } ], "require": { "doctrine/orm": "*", "symfony/yaml": "*", "pear-pear/Log": "*", "smarty/smarty" : "3.1.17" } } .. and run the command composer install . Or composer update if dependencies list updated. It creates a folder named vendor and all you project dependencies are there. You just have to include vendor/autoload.php and start coding. If you still do not use it, I really recommend it. Homepage can be found here .