Get Real IP Address of site visitor

Most of us should be relying on the server side environmental variable REMOTE_ADDR solely for client IP addresses

Yet it’s barely enough to get the real IP for a variety of circumstances such as when the user is visiting your website from a proxy server. To everyone’s surprise, there are a lot more environmental variables regarding client IP address than just the most straightforward one, REMOTE_ADDR. Consider this snippet in the attempt to detect the real source IP address of the request:

function get_ip_address() {

foreach (array('HTTP_CLIENT_IP', 'HTTP_X_FORWARDED_FOR', 'HTTP_X_FORWARDED', 'HTTP_X_CLUSTER_CLIENT_IP', 'HTTP_FORWARDED_FOR', 'HTTP_FORWARDED', 'REMOTE_ADDR') as $key) {

    if (array_key_exists($key, $_SERVER) === true) {
       foreach (explode(',', $_SERVER[$key]) as $ip) {
         if (filter_var($ip, FILTER_VALIDATE_IP) !== false) {
           return $ip;
           }
         }
       }
    }
}

'HTTP_CLIENT_IP', 'HTTP_X_FORWARDED_FOR', 'HTTP_X_FORWARDED', 

'HTTP_X_CLUSTER_CLIENT_IP', 'HTTP_FORWARDED_FOR',

 'HTTP_FORWARDED', 'REMOTE_ADDR' 

these are possible environmental variables that may contain the client 

IP address. You better not change the order these variable names are 

placed in the literal array.

We are using this approach because If your client is connected to the 

Internet through Proxy Server then 
$_SERVER['REMOTE_ADDR'] in PHP just returns the the IP address of the 
proxy server not of the client’s machine.

In other way we can write like this

function getRealIpAddr()
{
    if (!empty($_SERVER['HTTP_CLIENT_IP']))   //check ip from share internet
    {
      $ip=$_SERVER['HTTP_CLIENT_IP'];
    }
    elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR']))   //to check ip is pass from proxy
    {
      $ip=$_SERVER['HTTP_X_FORWARDED_FOR'];
    }
    else
    {
      $ip=$_SERVER['REMOTE_ADDR'];
    }
    return $ip;
}

In this PHP function, first attempt is to get the direct IP address of 
client’s machine, if not available then try for forwarded for IP address
 using HTTP_X_FORWARDED_FOR. And if this is also not available, then 
finally get the IP address using REMOTE_ADDR

PHP Functions available to detect IP address

PHP function - $REMOTE_ADDR

PHP function - $REMOTE_HOST

PHP function - $HTTP_X_FORWARDED_FOR

PHP function - $HTTP_VIA

PHP function - $HTTP_CLIENT_IP

PHP function - $HTTP_PROXY_CONNECTION

PHP function - $FORWARDED_FOR

PHP function - $X_FORWARDED_FOR

PHP function - $X_HTTP_FORWARDED_FOR

PHP function - $HTTP_FORWARDED