php获取客户端ip

/**

     * 获取客户端ip

     * @return string

     */

    public static function get_ip(){

        static $realip = NULL;

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

        if (isset($_SERVER)) {

            if(isset($_SERVER['HTTP_X_REAL_IP']) && $_SERVER['HTTP_X_REAL_IP']){

                $realip = $_SERVER['HTTP_X_REAL_IP'];

            }elseif (isset($_SERVER['HTTP_X_FORWARDED_FOR']) && $_SERVER['HTTP_X_FORWARDED_FOR']) {

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

                foreach ($arr AS $ip) {

                    $ip = trim($ip);

                    if ($ip != 'unknown') {

                        $realip = $ip;

                        break;

                    }

                }

            } elseif (isset($_SERVER['HTTP_CLIENT_IP']) && $_SERVER['HTTP_CLIENT_IP']) {

                $realip = $_SERVER['HTTP_CLIENT_IP'];

            } else {

                $realip = isset($_SERVER['REMOTE_ADDR']) ? $_SERVER['REMOTE_ADDR'] : '0.0.0.0';

            }

        } else {

            if (getenv('HTTP_X_REAL_IP')){

                $realip = getenv('HTTP_X_REAL_IP');

            }elseif (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');

            }

        }

        $onlineip = array();

        preg_match("/[\\d\\.]{7,15}/", $realip, $onlineip);

        return !empty($onlineip[0]) ? $onlineip[0] : '0.0.0.0';

    }