PHP REST API

Hi !
This week I thought about the best way to build REST API with PHP , assuming server constraints. The context is that, I work with startups and incubators as technical advisor and sometimes as #fullstack developer. Some of those startups use mutualised server (shared hosting , no VPS); so they don't have hand in infrastructure configuration.
I present them different ways as : codeIgniter as a framework with zero constraint that requires VPS as production server. No need of composer, there is no cli commands.
But the REST request is not natively handled. There are some issues with PHP//input.
And for symfony it recommended to use VPS as Prod server.
I need your point of view , and advise for optimisation and configuration.