Unfortunately I\'ve reached a bit of a dead end. Due to various legacy and other reasons, I can\'t upgrade a system to PHP 5.4. And according to Facebook, I need 5.4 to run
You can still use the old one: https://github.com/facebookarchive/facebook-php-sdk
The api calls are the same. The new one is just the recommended one. You can even use your own CURL calls without any SDK.
You should use the latest one though, it may be a good idea to change your provider. PHP 5.4 should be an absolute minimum every serious provider supports.
For the old PHP, you don´t really need composer. Just download it and put in your server.