php - 基于概率从PHP数组中选择随机项目

Question

我有一张用户 map 以及他们为抽奖(或彩票或任何其他类似事件)购买的条目/门票数量。

用户到条目的映射结构如下所示:

// Map the person to the amount of entries they have purchased
$entries = [
    'Adam' => 5,
    'James' => 3,
    'Oliver' => 4,
    'Holly' => 8
];

我想选择一个随机用户，但根据票数考虑他们的机会。获胜的概率必须是:

(User Ticket Amount / Total Ticket Count) * 100 = Probability percentage

例如，从测试数组来看，预期结果是 Holly 将赢得 20 次抽奖中的 8 次。

Answer 1

前几天为博彩网站编写脚本时，我创建了一种方法来执行此操作，因此您会问这个问题是巧合。

请参阅注释以解释代码的组成:

// The array passed to the function should be your $entries array
function randProb(array $items) {
  $totalProbability = 0; // This is defined to keep track of the total amount of entries

  foreach ($items as $item => $probability) {
      $totalProbability += $probability;     
  }

  $stopAt = rand(0, $totalProbability); // This picks a random entry to select
  $currentProbability = 0; // The current entry count, when this reaches $stopAt the winner is chosen

  foreach ($items as $item => $probability) { // Go through each possible item
      $currentProbability += $probability; // Add the probability to our $currentProbability tracker
      if ($currentProbability >= $stopAt) { // When we reach the $stopAt variable, we have found our winner
          return $item;
      }
  }

  return null;
}

有任何问题欢迎在下方提问，如果您想输出中奖元素的值(value)(概率)，返回 $probability在断点而不是 $item