How to create a app embed blocks and call in the theme (under theme app extension) by php

[chetna]

Hello 

I am creating a Shopify App by using PHP language.Before theme app extension we using the asset.json end point to insert our snippets files in the theme from our app.But after coming the theme app extension framework ,I don't know how to create a app embbed blocks file and call in for our shopify app.so my app enable/disable option comes in the theme customize>app embbed section

There is no any documentation for php based app embbed blocks so please help me to do this .

Thank you