PSX is a framework written in PHP which helps

to build clean and documented REST APIs.

PSX provides tools to handle common API tasks like data serialization, validation, documentation, API versioning and testing. So you can concentrate on building the actual business logic of your API. Some reasons you might want to use PSX:

Automatic documentation generation

Generate controller and model classes from a schema API specification

Work with POPOs for incoming and outgoing data

for incoming and outgoing data Automatic generation of schema specifications (OpenAPI, RAML)

Validate incoming data based on TypeSchema

Based on multiple independent components

Please take a look at the getting started tutorial for a step by step guide how to build an API based on a database.