获取ip地址

/**
 * 获取ip地址
**/
function get_ip(){
    $real_ip = '';
    $unknown = 'unknown';
    if (isset($_SERVER)){
        if(isset($_SERVER['HTTP_X_FORWARDED_FOR']) && !empty($_SERVER['HTTP_X_FORWARDED_FOR']) && strcasecmp($_SERVER['HTTP_X_FORWARDED_FOR'], $unknown)){
            $arr = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
            foreach($arr as $ip){
                $ip = trim($ip);
                if ($ip != 'unknown'){
                    $real_ip = $ip;
                    break;
                }
            }
        }else if(isset($_SERVER['HTTP_CLIENT_IP']) && !empty($_SERVER['HTTP_CLIENT_IP']) && strcasecmp($_SERVER['HTTP_CLIENT_IP'], $unknown)){
            $real_ip = $_SERVER['HTTP_CLIENT_IP'];
        }else if(isset($_SERVER['REMOTE_ADDR']) && !empty($_SERVER['REMOTE_ADDR']) && strcasecmp($_SERVER['REMOTE_ADDR'], $unknown)){
            $real_ip = $_SERVER['REMOTE_ADDR'];
        }else{
            $real_ip = $unknown;
        }
    }else{
        if(getenv('HTTP_X_FORWARDED_FOR') && strcasecmp(getenv('HTTP_X_FORWARDED_FOR'), $unknown)){
            $real_ip = getenv("HTTP_X_FORWARDED_FOR");
        }else if(getenv('HTTP_CLIENT_IP') && strcasecmp(getenv('HTTP_CLIENT_IP'), $unknown)){
            $real_ip = getenv("HTTP_CLIENT_IP");
        }else if(getenv('REMOTE_ADDR') && strcasecmp(getenv('REMOTE_ADDR'), $unknown)){
            $real_ip = getenv("REMOTE_ADDR");
        }else{
            $real_ip = $unknown;
        }
    }
    $real_ip = preg_match("/[\d\.]{7,15}/", $real_ip, $matches) ? $matches[0] : $unknown;
    return $real_ip;
}