I have a project running on Apigility + Doctrine. From a scratch (automatically without writing extra code), I can retrieve entities and collections with pagination, filtering, etc.
This is perfect when retrieving DB rows, however, most services need to return much more data. For example: a to-do list where the "tasks" have parents, if you want to retrieve this like a tree, you´ll have to process it first. Very often I need flags to tell the frontend how to process data or keys to display or hide stuff. Sometimes it is useful to retrieve extra information that is not expressed in the database as FK or PK, etc.
So far, with Apigilty+Doctrine, if I want to add ANY information to the output, I have to modify the Entity, set up the correct keys, and it works. However, from the previous examples you can see that the data that I need is NOT coming from the database or I cannot simply express the relation as a DB dependency.
Questions:
By default, the Entity values will be given as response as is. If you want to modify the value (eg: retrieving parent data, retrieving child data, or modifying the data format) you should create a Hydrator for this Entity, and custom Hydrator Strategy for this Entity value.
Here is Hydrator example from my Apigility and Doctrine project