PHP lottery algorithm case

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][&#39;prize&#39;]; //未中奖项数组 
    }  
    $res[&#39;no&#39;] = $pr; 
    // var_dump($res);
 
      
    if($res[&#39;yes&#39;]!=&#39;空奖&#39;){ 
      $result[&#39;status&#39;]=1; 
      $result[&#39;name&#39;]=$res[&#39;yes&#39;]; 
    }else{ 
      $result[&#39;status&#39;]=-1; 
      $result[&#39;msg&#39;]=$res[&#39;yes&#39;]; 
    }  
    //return $result; 
    var_dump($result);
  } 
 
  //计算中奖概率
  function get_rand($proArr) {  
   $result = &#39;&#39;;  
   //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;  
  }