How much of a hassle is it to come up with a PHP function of some kind that can check an IP to see if it's within a specified CIDR range?

Say you get something like this:

I have a persistent spammer I've banned individual IPs from. The IPs I keep getting all fall within the CIDR value the network info shows. I'd like to input the CIDR value for the banned IP and be done with the problem for good. Or at least put a serious crimp in his plan. How would I go about this in php to check if the IP connecting to the site falls within the range?

I know I could just input that into iptables instead and be done with it, but all I want to do is stop the fool abusing our site from being able to register ( and therefore post ) and I'd rather not fill up the firewall with a bunch of crud.

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Well, me being clueless and not knowing what a CIDR value is, I might not know how to answer your question...what is a CIDR value?

Either way, if you want to ban all 68.240.x.x IP's and therefore stop registrations from that IP, you can do that...probably by putting 68.240.*.* into the ban list.

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