Checking out a versioned Symfony Application
When using Composer to manage application’s dependencies, it’s recommended to ignore the entire vendor/ directory before committing its code to the repository. This means that when checking out a Symfony application from a Git repository, there will be no vendor/ directory and the application won’t work out-of-the-box.
In order to make it work, check out the Symfony application and then execute the install Composer command to download and install all the dependencies required by the application:
$ cd my_project_name/ $ composer install
How does Composer know which specific dependencies to install? Because when a Symfony application is committed to a repository, the composer.json and composer.lock files are also committed. These files tell Composer which dependencies (and which specific versions) to install for the application.