I am currently working on a fairly old website service for the company's internal needs. The stack is quite old - PHP 5.3. It so happened that company can't abandon it right now.

... In short, I received a task to develop a REST API for this service. It is clear that I cannot use the current stack. What can I use as a standalone core for the new API? The main thing for me is the speed of development and ease of learning. For example, I would like Bearer authorization / some rights model out of box.

Something like Laravel, but separate instance of it just for the API seems a little overkill for me. What you can advise me? Any boilerplates / software recommendations are welcomed.

PS: My database is MSSQL 2016, so it could be a problem.