How to use variables in my PHP website header file.

Hello,

I'm trying to use PHP variables so that I can use my header file to display the menu on all my webpages, however, I wanted to be able to change a line of text on each page by setting a variable for the php header to use for each page so for example:

I have my php header file and in it I have a the line

Company Name - <?php $var ?>

and on each individual page I have something like:

does anyone have any ideas why this may not be working? Or any ideas on a different approach to this?

Thanks in advance

-CK