In php.ini, there is this:
; Decides whether PHP may expose the fact that it is installed on the server
; (e.g. by adding its signature to the Web server header). It is no security
; threat in any way, but it makes it possible to determine whether you use PHP
; on your server or not.
expose_php = On
What this means is that for every request that calls on PHP, it sends an additional header that looks something like this:
With PHP, it’s all or bust. Not PHP/5 or just PHP. You can overwrite every version by doing something like:
<?php header("X-Powered-By: Cookies-and-Sess/2.5"); ?>
Or something similar, but you have to do it manually for every script. There isn’t really a server wide override.