聊聊TP在app接口开发过程中的安全验证问题

<?php
namespace Home\Controller;
use Think\Controller;
class IndexController extends Controller {
    public $appid = 'dmm888';    
    public $appsecret = 'http://cnblogs.com/dmm888';
    
    public function index(){
        $this->show('<style type="text/css">*{ padding: 0; margin: 0; } div{ padding: 4px 48px;} body{ background: #fff; font-family: "微软雅黑"; color: #333;font-size:24px} h1{ font-size: 100px; font-weight: normal; margin-bottom: 12px; } p{ line-height: 1.8em; font-size: 36px }</style><div style="padding: 24px 48px;"> <h1>:)</h1><p>欢迎使用 <b>ThinkPHP</b>！</p><br/>[ 您现在访问的是Home模块的Index控制器 ]</div><script type="text/javascript" src="http://tajs.qq.com/stats?sId=9347272" charset="UTF-8"></script>','utf-8');
    }
    public function  test(){
        if(!isset($_GET['token'])){
            $this->apiReturn(4001,'invalid token');
        }else if(!S($_GET['token'])){            
            $this->apiReturn(4001,'invalid token');
            
        }
 
        $data = array(
            'id'=>2,
            'username'=>'明之暗夜',
            'info'=>array('age'=>24,'address'=>'学府路','url'=>'http://cnblogs.com/dmm888')
        );
        if($data){
            $this->apiReturn(200,'读取用户信息成功',$data,xml);
        }
    }
    public function getToken(){
        $ori_str = S($this->appid.'_'.$this->appsecret);   //这里appid和appsecret我写固定了，实际是通过客户端获取  所以这里我们可以做很多 比如判断appid和appsecret有效性等
        if($ori_str){       //重新获取就把以前的token删除
            S($ori_str,null);
        }
        //这里是token产生的机制  您也可以自己定义
        $nonce = $this->createNoncestr(32);
        $tmpArr = array($nonce,$this->appid,$this->appsecret);
        sort($tmpArr, SORT_STRING);
        $tmpStr = implode( $tmpArr );
        $tmpStr = sha1( $tmpStr );
        // echo $tmpStr;
        //这里做了缓存 'a'=>b 和'b'=>a格式的缓存
        S($this->appid.'_'.$this->appsecret,$tmpStr,7200);  
        S($tmpStr,$this->appid.'_'.$this->appsecret,7200);
    }
     /**
     *  作用：产生随机字符串，不长于32位
     */
     function createNoncestr( $length = 32 ) 
    {
        $chars = "abcdefghijklmnopqrstuvwxyz0123456789";  
        $str ="";
        for ( $i = 0; $i < $length; $i++ )  {  
            $str.= substr($chars, mt_rand(0, strlen($chars)-1), 1);  
        }  
        return $str;
    }     
}