PHP限制频繁请求

<?php
header("Content-Type:text/html; charset=utf-8");
 

include_once("libs/RSA.class.php");
/**
 * 在线高频频繁提交解决方案
 * @author 周阳<305846826@qq.com>
 * @link http://www.jieone.com/
 */
class Token extends RSA{
	/**
	 * 客户端唯一ID
	 */
	private $date=0;
	
	private $clientID="abccccc";
	/**
	 * 系统access_token，即要保存于客户端的数据
	 */
	private function sys_access_token(){
		$array=array(
				'clientID'=>$this->clientID,
				'date'=>$this->date
				);
		$sys_access_token = json_encode($array);
		//RSA公钥加密
		return $this->public_encrypt($sys_access_token);
	}
	/**
	 * 保存access_token
	 */
	public function get_access_token(){
		
		 if(empty($_COOKIE['access_token'])){
			 $this->date=time()-100;
			return $this->sys_access_token(); 
		 }
		 return $_COOKIE['access_token'];
	}
	/**
	 * 保存access_token
	 */
	private function save_access_token(){
		
		setcookie("access_token",$this->sys_access_token());	
	}
	
	public function check(){
		
		$access_token=$this->get_access_token();
		
		//RSA私钥解密
		$access_token = $this->private_decrypt($access_token);
		
		//信息已被非法篡改
		if(empty($access_token)){
			return false;
		}
		
		$object=json_decode($access_token);

		//2秒只能ajax请求一次,可修改
		if ($object->date + 2 > time()){
			return false;
		}
		//保存access_token
		$this->date=time();
		$this->save_access_token();
		return true;	
	}
		
}

echo '<br><br><br><br><br><br><center><h1>频繁刷新试试</h1></center><br>';

$Token=new Token();
if(!$Token->check()){
	echo '<center><h2 style=" color:red">您请求过快，请稍后再试</h2></center><br><br><br>';
	exit();
}
echo '<center><h2 style=" color:green">访问正常</h2></center><br><br><br>';

echo "您当前access_token:".$Token->get_access_token();