API Platform is a framework to build APIs on top of symfony. Used by very large companies across the world, it is very powerful and allows to create feature-rich APIs. Following what made Symfony itself so successful, API Platform offers great documentation and enterprise-grade suport.
It comes with with a total of 4 components that can be used separately from each other, with the API component being the most important one. It allows developers to create standard-confom REST and GraphQL APIs with OpenAPI (formerly Swagger) documentation. The technical foundation is both robust and performant and allows to create and customize APIs the way it should be. API patform can both be used to expose your apps business logic very easily as an API or, even better - model your public APIs independent from your internal business logic.
The Admin generator, another component of API platform, creates very basic admin interfaces with CRUD operations using the generated API of the core module. The generated code is written in React and can easily be customized. In the current stage, the admin generator cannot compete with the more powerful easyadmin, but it's a very good starting point and might be enough for smaller CRUD based applications.
If your API will be consumed in one of the big frontend frameworks, API platform got you covered too. The client generator uses your API definition and generates scaffolding apps for Next.js, Nuxt.js, Vuetify, Quasar, React, Vue.js or React Native.