In the context of PHP, what alternative method can be used to successfully obtain the hostname of the client when $_SERVER["REMOTE_HOST"] does not return any results?

When $_SERVER["REMOTE_HOST"] does not return any results, an alternative method to obtain the hostname of the client is to use the gethostbyaddr() function. This function takes the client's IP address as a parameter and returns the corresponding hostname if available. By using gethostbyaddr() as a fallback option, you can still retrieve the client's hostname even if $_SERVER["REMOTE_HOST"] is not providing the desired information.

$client_ip = $_SERVER['REMOTE_ADDR'];
$client_hostname = gethostbyaddr($client_ip);

echo "Client IP: " . $client_ip . "<br>";
echo "Client Hostname: " . $client_hostname;