Thanks for reply.
SSI seemed to only work if an “include” was added to pages.
Using php_value in Apache or the file append in php.ini seemed the best options.
Also briefly looked at AddOutputFilter/Substitute and the cgi options. Did not explore mod_layout very closely.
Google Analytics, by default, only tracks pages by path.
Meaning if you add a Google Analytics snippet to all virtual hosts visitors to the home page of each site will be almost impossible to distinguish from each other in the reports...there are ways around this
but you should be aware of it.
I believe you'll want to review the documentation for server side includes (SSI).