公平的資料庫獎項抽獎

GiftShuffer.php

<?php 

  /*
    0      4      4        4               7           10000    15300        17200
    | 金槌 | 手機 | 吹風機 | Coach 隨手包  | ... | ... | 環保筷 | 商品抵用券 |
                                                         ↑ ( 隨機數字 12345 )
  */

  class GiftShuffler {

    private $randsamples = array();
    private $samplestotal = 0; 

    function __construct($db){
      $rows=$db->rows("select * from gifttable");
      foreach($rows as $gift){
        array_push($this->randsamples, array(
          'id' => $gift['id'],
          'name' => $gift['name'],

          // 建立獎項分配數線
          'rangeFrom' => $this->samplestotal, 
          'rangeTo' => $this->samplestotal + $gift['total'] - $gift['hasget'], // 可中獎長度必須扣掉已送出的數量

          'dailyTotal' => $gift['dailyget'],
          'dailySent' => ($gift['pagedate'] == date('Y-m-d')) ? $gift['hasdailyget'] : 0, //如果 pagedate 是今天，表示 hasdailyget 代表今天所送出
          'lastSent' =>$gift['pagedate'],

          'total' => $gift['total'],
          'totalSent' => $gift['hasget']
        ));
        // 紀錄數線終點
        $this->samplestotal += ($gift['total'] - $gift['hasget']);
      }
    }

    public function sample(){
      $get = mt_rand(0, $this->samplestotal-1);
      foreach ($this->randsamples as $gift) {
        //如果隨機數字在獎項的區段，那就是這個獎項了
        if($get >= $gift['rangeFrom'] and $get < $gift['rangeTo']){
          if($gift['dailySent'] >= $gift['dailyTotal']){
            return false; // 本日獎項已配送完
          }
          return $gift;
        }
      }
      return false;
    }  
  }

  $shuffler = new GiftShuffler($db);
  $gift = $shuffler->sample();