We use composer to install PHP dependencies. These are defined in the file composer.json, the current dependency metadata is in composer.lock.
To fetch the dependencies:
- Get composer.phar as described at https://getcomposer.org/download/
- run [path_to]/composer.phar install in the webroot.
This will install all required dependencies to the directory vendor. The vendor directory is listed in .gitignore to avoid committing duplicates of upstream projects.