I am trying to include a php file, which has both the php

Hello,
I am trying to include a php file, which has both the php and html code embedded in it.
I treid to go through different pages, amberpanther plugin is not available, and include me is not working too. Please guide me.

I can't separate the code into php and html parts to add in the widgets. Can you help me with it.

Second, if I want to load a file in public_html, is it the the correct syntax. or do I have to add the ABSPATH in this case prior to loading a file
$someFile = 'some-simple.txt'; // some file

Thank you