нормальное определение реального IP за прокси Opera, UcWeb, Ovi и т.п., где используется сжатие трафика.
Использовать: echo getRealIP();

                        
function getRealIP() {

  $result = false;

  $proxy_headers = array(

    'CLIENT_IP', 

    'FORWARDED', 

    'FORWARDED_FOR', 

    'FORWARDED_FOR_IP', 

    'HTTP_CLIENT_IP', 

    'HTTP_FORWARDED', 

    'HTTP_FORWARDED_FOR', 

    'HTTP_FORWARDED_FOR_IP', 

    'HTTP_PC_REMOTE_ADDR', 

    'HTTP_PROXY_CONNECTION',

    'HTTP_VIA', 

    'HTTP_X_FORWARDED', 

    'HTTP_X_FORWARDED_FOR', 

    'HTTP_X_FORWARDED_FOR_IP', 

    'HTTP_X_IMFORWARDS', 

    'HTTP_XROXY_CONNECTION', 

    'VIA', 

    'X_FORWARDED', 

    'X_FORWARDED_FOR'

  );



  foreach($proxy_headers as $proxy_header) {

    if ($result !== false) continue;

      if(isset($_SERVER[$proxy_header])) {

    preg_match("/d{1,3}.d{1,3}.d{1,3}.d{1,3}/", $_SERVER[$proxy_header],$matches);

    if (isset($matches[0])) {

      $result = $matches[0];

      continue;

    }

    }

    else if(stristr(',', $_SERVER[$proxy_header]) !== FALSE) {

      $proxy_header_temp = trim(array_shift(explode(',', $_SERVER[$proxy_header]))); 

      if(($pos_temp = stripos($proxy_header_temp, ':')) !== FALSE) $proxy_header_temp = substr($proxy_header_temp, 0, $pos_temp); 

      if(preg_match("/^([1-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])(.([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])){3}$/", $proxy_header_temp)){

        $result = $_SERVER[$proxy_header];

        continue;            

      }   

    }

  }

  

  if ($result === false){

    $result = $_SERVER['REMOTE_ADDR'];

  }

  if (preg_match("#([0-9]+.).*#", $result, $m)){

    if ($m[1] == "10." || $m[1] == "100."){

      $result = $_SERVER['REMOTE_ADDR'];

    }

  }

  if (preg_match("#([0-9]+.[0-9]+.).*#", $result, $m)){

    if ($m[1] == "192.168."){

      $result = $_SERVER['REMOTE_ADDR'];

    }

  }

  return $result;

};