Implementing site access rate limiting in PHP

I am developing a fairly simple site on a LAMP framework + Codeigniter and want to implement a user access rate limit feature to prevent the site being flooded with requests from a single user. The basic function of the site is to take a code input and return some info.

I'm only at the planning stages and my first idea is to have a simple database table holding an IP address, last access timestamp and an access count, but as my coding skills are rooted in non web-based apps I would appreci开发者_如何学JAVAate any thoughts on the best way to approach this task - for example, should I be considering session IDs instead of, or as well as, IP addresses?

I've not found much with some general Web searches so any pointers or guidance would be great.

Thanks.

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If you really need to do this, you're probably better off doing it before PHP even gets involved. You might consider looking into configuring a router or load-balancer to do this, or at the very least, some kind of web-server module.

Doing this in PHP is likely to create so much overhead as to be self-defeating.