PHP:real_ip(得到用户的真实IP)

PHP:real_ip

/** 
* 获得用户的真实IP地址 
* 
* @access  public 
* @return  string 
*/ 
function real_ip() 
{ 
    static $realip = NULL; 

    if ($realip !== NULL) 
    { 
        return $realip; 
    } 

    if (isset($_SERVER)) 
    { 
        if (isset($_SERVER['HTTP_X_FORWARDED_FOR'])) 
        { 
            $arr = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']); 

            /* 取X-Forwarded-For中第一个非unknown的有效IP字符串 */ 
            foreach ($arr AS $ip) 
            { 
                $ip = trim($ip); 

                if ($ip != 'unknown') 
                { 
                    $realip = $ip; 

                    break; 
                } 
            } 
        } 
        elseif (isset($_SERVER['HTTP_CLIENT_IP'])) 
        { 
            $realip = $_SERVER['HTTP_CLIENT_IP']; 
        } 
        else 
        { 
            if (isset($_SERVER['REMOTE_ADDR'])) 
            { 
                $realip = $_SERVER['REMOTE_ADDR']; 
            } 
            else 
            { 
                $realip = '0.0.0.0'; 
            } 
        } 
    } 
    else 
    { 
        if (getenv('HTTP_X_FORWARDED_FOR')) 
        { 
            $realip = getenv('HTTP_X_FORWARDED_FOR'); 
        } 
        elseif (getenv('HTTP_CLIENT_IP')) 
        { 
            $realip = getenv('HTTP_CLIENT_IP'); 
        } 
        else 
        { 
            $realip = getenv('REMOTE_ADDR'); 
        } 
    } 

    preg_match("/[\d\.]{7,15}/", $realip, $onlineip); 
    $realip = !empty($onlineip[0]) ? $onlineip[0] : '0.0.0.0'; 

    return $realip; 
}