Here are a few major resource-saving updates that require attention:
• All of the "SELECT *" database calls need to be replaced by "SELECT this, that" except in the rare situations where "SELECT *" is necessary.
• The database connections need to be left on, rather than connecting, disconnecting and reconnecting, only to disconnect and reconnect again.
• That "framework" desperately needs to be gotten rid of. arpReach would run a lot lighter if it was its own stand-alone program, rather than relying on third-party scripts, like CodeIgnitor, or whatever that is.
Of course, without being able to see the code, I am only guessing as to how it is written. But being that it loads so heavily in memory (a single page can load up to 20 MB in memory) and that the first copyright year on the bottom of the main site is 2000, at least a couple of these guesses must be accurate.
Whichever of these guesses are correct (obviously the framework one is), I hope that you will attend to them in a future update. On the main site is advertised that arpReach is compatible with shared hosting accounts. In fact, most shared hosts will lower your memory limit for running this script because it requires too much. I have already had this happen at two shared hosts.