PHP获取用户访问IP地址的5种方法

<?php                                                                 //方法1：$ip = $_SERVER["REMOTE_ADDR"];echo $ip; //方法2：$user_IP = ($_SERVER["HTTP_VIA"]) ? $_SERVER["HTTP_X_FORWARDED_FOR"] : $_SERVER["REMOTE_ADDR"];$user_IP = ($user_IP) ? $user_IP : $_SERVER["REMOTE_ADDR"];echo $user_IP; //方法3：function getRealIp(){  $ip=false;  if(!empty($_SERVER["HTTP_CLIENT_IP"])){    $ip = $_SERVER["HTTP_CLIENT_IP"];  }  if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {    $ips = explode (", ", $_SERVER['HTTP_X_FORWARDED_FOR']);    if ($ip) { array_unshift($ips, $ip); $ip = FALSE; }    for ($i = 0; $i < count($ips); $i++) {      if (!eregi ("^(10│172.16│192.168).", $ips[$i])) {        $ip = $ips[$i];        break;      }    }  }  return ($ip ? $ip : $_SERVER['REMOTE_ADDR']);}echo getRealIp(); //方法4：if ($HTTP_SERVER_VARS["HTTP_X_FORWARDED_FOR"]){  $ip = $HTTP_SERVER_VARS["HTTP_X_FORWARDED_FOR"];}elseif ($HTTP_SERVER_VARS["HTTP_CLIENT_IP"]){  $ip = $HTTP_SERVER_VARS["HTTP_CLIENT_IP"];}elseif ($HTTP_SERVER_VARS["REMOTE_ADDR"]){  $ip = $HTTP_SERVER_VARS["REMOTE_ADDR"];}elseif (getenv("HTTP_X_FORWARDED_FOR")){  $ip = getenv("HTTP_X_FORWARDED_FOR");}elseif (getenv("HTTP_CLIENT_IP")){  $ip = getenv("HTTP_CLIENT_IP");}elseif (getenv("REMOTE_ADDR")){  $ip = getenv("REMOTE_ADDR");}else{  $ip = "Unknown";}echo $ip ; //方法5：if(getenv('HTTP_CLIENT_IP')) {  $onlineip = getenv('HTTP_CLIENT_IP');} elseif(getenv('HTTP_X_FORWARDED_FOR')) {  $onlineip = getenv('HTTP_X_FORWARDED_FOR');} elseif(getenv('REMOTE_ADDR')) {  $onlineip = getenv('REMOTE_ADDR');} else {  $onlineip = $HTTP_SERVER_VARS['REMOTE_ADDR'];}echo $onlineip;