Checks if an (compressed) IP is in a specific address space. If the IP does not contain the number of netmask bits (for example: F8000::FFFF/16), then you have to use the $bits parameter.
string $ip - the IP address in Hex format, compressed IPs are allowed
string $netmask - the netmask (for example: F800::)
int $bits - if the number of netmask bits is not part of the IP, you must provide the mumber of bits