Required PHP modules?

Greetings!

Are there specific PHP modules that need to be installed and configured? On our test site, I can see the debugging details for a logged in user:
<!– GD Booster is NOT caching this page, because the current user visiting this page (usually YOU), appears to be logged-in. The current configuration says NOT to cache pages for logged-in visitors. This message may also appear if you have an active PHP session on this site, or if you’ve left (or replied to) a comment recently. If this message continues, please clear your cookies and try again. –>

But for a non-logged in user, I do not see any feedback what so ever. I do find notes above in the code about moved/processed CSS and JS files, but nothing about a quick cache file.

I’ve checked the file permissions for the cache folder, and they are set to 755.

We are using a dedicated server running WHM that may not have any caching modules installed and configured.

Thanks for your help!