We are going to make use of three environment variables of PHP in order to code this simple PHP class that returns the real IP address of a visitor, even when connecting via a proxy. The three PHP environment variables we`ll use are

HTTP_CLIENT_IP:  gets the IP address of  Internet Service Provider.

HTTP_X_FORWARDED_FOR: gets the ip if the request is passed from a proxy. It will be empty if the pass is from a proxy.

REMOTE_ADDR: gets the IP address of  requesting client.

Now, with all the all the required variables explained let us code our PHP class.

function real_ip_address() {

	if (!empty($_SERVER['HTTP_CLIENT_IP'])){     //check if ip is from ISP
		$ip = $_SERVER['HTTP_CLIENT_IP'];
	}
	elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])){     //check if ip is passed from a proxy
		$ip = $_SERVER['HTTP_X_FORWARDED_FOR'];
	}
	else{
		$ip = $_SERVER['REMOTE_ADDR'];
	}
	return $ip;
}

Now, the question is how to use this class? Copy the above code and paste it in a text file between the <?php - ?> tags. Save the file as realipaddress.php and place in your document root. Include this php file in your other code files by writing the statement

include('realipaddress.php');

Now you can get the client`s IP address stored in a variable called $ip