Review on the files the main functions are deprecated/removed on 2011-2012 by php.
The files creation time say 2015 but this is not true they are older, much older than 2011 and so badly written that every single query can be SQL Injected.
Code style bad for eyes.
Connections for database are so many without any caching.
No object oriented code anywhere just functions thrown here and there.
no error handler
I should not continue, amateurs..
My conclusion: This is an example of how NOT to code something in any programming language, plus it misses essential files.
Note: The image is misleading its not the current version of topzone
Note: Files are just for museum
https://www.virustotal.com/gui/file/c115a8aa0768c6fea9c75d5144671b1167d51956376f6b8498f345b1e9a30e0d/detection