SSI not working as expected

Hi,

I’m trying to create a navbar that I can reuse but I’m having issues. I created a file called header.php and moved it to Include file. Then on index.php I add SSI as PHP Include.

header.php

index.php

what am I doing wrong?

So this issue is the colour change?
May be way off target but visually i am guessing there is a CSS problem.
Check the paths to your custom CSS file, assuming you are using one. Have you saved the SSI in a subdirectory and broken the CSS paths?