How to get facebook group id via facebook php sdk?

Question

PHP

Good afternoon !
Please tell me how to get the id of a group or post through php sdk
Suppose I have only a link:
facebook.com/group_name
I understand what can be written in the address bar graph.facebook.com/group_name
and I will see the data (id) of interest to me,
but I this must be done through the php
function of the type - getId ($ link) which will return only the id
and another question - how to get the same id but the post ....