How to detect subnet IP? [closed]

Answer 1

PHP has bulit-in mechanism to validate some common types, for your case it would be:

$isIP = filter_var($ip, FILTER_VALIDATE_IP);

$isSubnet = !filter_var($ip, FILTER_VALIDATE_IP, 
    FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE
);

return $isIP && $isSubnet;

You can use FILTER_FLAG_IPV4/6 in first check as third parameter to ensure desired format.