Checking if a POST[] variable is an IP address?

Question

I'm making a script, in which the user needs to enter a valid IP address. How can I check that it's a valid IP address? (Doesn't need to resolve)

Basically $_POST['ip'] just needs to be between 0.0.0.0 and 255.255.255.255

Answer 1

If you're running PHP >= 5.2, use the Filter extension:

filter_var($ip, FILTER_VALIDATE_IP)

More info here and here.