PHP 关于获取客户端ip的方法

<?php 

/**
 * 获取ip地址的方法
 */

// 1：
function getip() {
  static $ip = '';
  $ip = $_SERVER['REMOTE_ADDR'];

  if(isset($_SERVER['HTTP_CDN_SRC_IP'])) {
    $ip = $_SERVER['HTTP_CDN_SRC_IP'];

  } elseif (isset($_SERVER['HTTP_CLIENT_IP']) && preg_match('/^([0-9]{1,3}.){3}[0-9]{1,3}$/', $_SERVER['HTTP_CLIENT_IP'])) {
    $ip = $_SERVER['HTTP_CLIENT_IP'];

  } elseif(isset($_SERVER['HTTP_X_FORWARDED_FOR']) AND preg_match_all('#d{1,3}.d{1,3}.d{1,3}.d{1,3}#s', $_SERVER['HTTP_X_FORWARDED_FOR'], $matches)) {
    foreach ($matches[0] AS $xip) {
      if (!preg_match('#^(10|172.16|192.168).#', $xip)) {
        $ip = $xip;
        break;
      }
    }

  }
  return $ip;
}

echo getip().'<hr>';


// 2:
error_reporting (E_ERROR | E_WARNING | E_PARSE);

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.'<hr>';


// 3：
$ip=$_SERVER['REMOTE_ADDR'];

echo $ip.'<hr>';


// 4:
$user_IP = ($_SERVER["HTTP_VIA"]) ? $_SERVER["HTTP_X_FORWARDED_FOR"] : $_SERVER["REMOTE_ADDR"];

$user_IP = ($user_IP) ? $user_IP : $_SERVER["REMOTE_ADDR"];

echo $user_IP.'<hr>';


// 5:
function get_real_ip(){

    $ip=false;
    if(!empty($_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 get_real_ip().'<hr>';


// 6:
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.'<hr>';
 ?>

如果访问者使用了代理或者是其它的情况，所取得的ip可能并不是真正的客户端ip