it is a php document that only has 2 variables that are hard-coded. It is a simple splash website that lets customers read about a product and lets them click to the actual product page. When I send 2000-4000 clicks within a 4-5 hour period the page doesn't load all the way because the high load! I do not have SSH access, only FTP. Anything I can do here?
Yeah if you are using sessions and the default time out is left as is, it will fill up your memory on the server and slow right down, set your session timeout value to a low number.
Which can be done with the info from here: How to change the session timeout in PHP?
There could be two possibilities:
a) since you have not SSH access I'll assume you're on a shared server, and if that's the case then 2000+ page loads for your site may be too much. You'd have to upgrade your hosting plan.
b) Too many session files for the server to handle. the server may be creating many sessions files as time passes and it keeps receiving more and more requests. To delete the sessions file you'd need SSH access or have the server admin do it for you.
If your server can't deal with 500+ requests an hour then you'd be better off just getting a better hosting plan.
Servers are not limitless, and normally, even higher grade private, self-managed machines, tend to be somewhat slow.