How do I check if a users input is a valid IP address or not?

Question

I want to check if an entered input is a valid IP address or not. I would like a specific function that will help me validate a users input.

Answer 1

By using preg_match();

function checkIPAddress($ipAddress) 
{
    return preg_match('/^(?:25[0-5]|2[0-4]\d|1\d\d|[1-9]\d|\d)(?:[.](?:25[0-5]|2[0-4]\d|1\d\d|[1-9]\d|\d)){3}$/', $ipAddress);
}