Answer 1

It might be under construction.

https://www.sololearn.com/discuss/3205664/?ref=app

Answer 2

There is a php course . https://www.sololearn.com/learn/courses/le-php

Answer 3

I don't believe there is a PHP course on offer at the moment, that's why you can't do it. You'll have to learn some other language and wait for the update, or look somewhere else.
There are some threads and codes here to give you resources for learning PHP.