php - 计算一个数组中某个值在另一个数组中出现的次数

Question

我有一组看起来像这样的人:

$people =
    Array
    (
        [0] => Array
            (
                [email] => NameSurname@example.com
                [name] => Name Surname
                [count] => 0
            )

        [1] => Array
            (
                [email] => Name2Surname@example.com
                [name] => Name2 Surname
                [count] => 0
            )
    )

我有一个数组，它是 MySQL 查询的结果，如下所示:

$query=
    Array
    (
        [0] => Array
            (
                [email] => NameSurname@example.com
                [name] => Name Surname
            )

        [1] => Array
            (
                [email] => Name2Surname@example.com
                [name] => Name2 Surname
            )

        [2] => Array
            (
                [email] => NameSurname@example.com
                [name] => Name Surname
            )

    )

对于 $people 中的每个电子邮件地址，我希望 $people['count'] 等于该电子邮件地址在 $query 中出现的次数。

我已经尝试了很多方法来做到这一点，但我并没有得到想要的结果。

为避免疑义，我基于上述示例的最终结果应如下所示:

$people =
    Array
    (
        [0] => Array
            (
                [email] => NameSurname@example.com
                [name] => Name Surname
                [count] => 2
            )

        [1] => Array
            (
                [email] => Name2Surname@example.com
                [name] => Name2 Surname
                [count] => 1
            )
    )

Answer 1

foreach ($people as $key => $man) { // iterating through each man
  $_occurences = 0;

  foreach ($query as $_item) // iterating through each result in the result set
    if ($_item['email'] == $man['email']) // comparing current man to each result item
      $_occurences ++;

  $people[$key]['count'] = $_occurences; // saving number of occurrences in the `count` key 

 }

---

更新:另一种解决方案使用array_map、array_reduce 和不错的三元 运算符。它比使用 foreach 的速度慢，但紧凑和专业的两倍。

因为它较慢(在性能方面)。函数调用的开销，但在“少量”迭代中，这种下降可以忽略不计。它会更新 $people 数组而不重新分配它。我们通过引用传输了每个 &$man。

array_map(function (&$man) use ($query) {
    $man['count'] = array_reduce($query, function ($count, $row) use ($man) {
        return ($row['email'] === $man['email']) ? ++$count : $count ;
    }, 0);
}, $people);