php 怎么实现大转盘功能

function get_gift(){  
        //拼装奖项数组 
        // 奖项id，奖品，概率
        $prize_arr = array(   
          '0' => array('id'=>1,'prize'=>'平板电脑','v'=>0),   
          '1' => array('id'=>2,'prize'=>'数码相机','v'=>0),   
          '2' => array('id'=>3,'prize'=>'音箱设备','v'=>0),   
          '3' => array('id'=>4,'prize'=>'4G优盘','v'=>5),   
          '4' => array('id'=>5,'prize'=>'10Q币','v'=>0),   
          '5' => array('id'=>6,'prize'=>'空奖','v'=>5),   
        );   
        foreach ($prize_arr as $key => $val) {   
          $arr[$val['id']] = $val['v'];//概率数组   
        }    
        $rid = $this->get_rand($arr); //根据概率获取奖项id   
        $res['yes'] = $prize_arr[$rid-1]['prize']; //中奖项   
        unset($prize_arr[$rid-1]); //将中奖项从数组中剔除，剩下未中奖项   
        shuffle($prize_arr); //打乱数组顺序   
        for($i=0;$i<count($prize_arr);$i++){   
          $pr[] = $prize_arr[$i]['prize'];  //未中奖项数组 
        }   
        $res['no'] = $pr; 
        // var_dump($res);
          
        if($res['yes']!='空奖'){  
            $result['status']=1;  
            $result['name']=$res['yes'];  
        }else{  
            $result['status']=-1;  
            $result['msg']=$res['yes'];  
        }   
        //return $result;  
        var_dump($result);
    }  
    //计算中奖概率
    function get_rand($proArr) {   
      $result = '';   
      //概率数组的总概率精度   
      $proSum = array_sum($proArr);   
      // var_dump($proSum);
      //概率数组循环   
      foreach ($proArr as $key => $proCur) {   
        $randNum = mt_rand(1, $proSum);  //返回随机整数 
        if ($randNum <= $proCur) {   
          $result = $key;   
          break;   
        } else {   
          $proSum -= $proCur;   
        }   
      }   
      unset ($proArr);   
      return $result;   
    }