如何在PHP中删除多维数组中的重复值（重新访问）

Question

如何从PHP的多维数组中删除重复值？

初始数组:

    array (
  0 => 
  array (
    'following_userid' => '88',
  ),
  1 => 
  array (
    'following_userid' => '89',
  ),
  2 => 
  array (
    'following_userid' => '287',
  ),
  3 => 
  array (
    'following_userid' => '346',
  ),
  4 => 
  array (
    'following_userid' => '405',
  ),
  5 => 
  array (
    'following_userid' => '284',
  ),
  6 => 
  array (
    'following_userid' => '583',
  ),
  7 => 
  array (
    'following_userid' => '587',
  ),
  8 => 
  array (
    'following_userid' => '655',
  ),
  9 => 
  array (
    'following_userid' => '95',
  ),
  10 => 
  array (
    'follower_userid' => '89',
  ),
  11 => 
  array (
    'follower_userid' => '88',
  ),
  12 => 
  array (
    'follower_userid' => '353',
  ),
  13 => 
  array (
    'follower_userid' => '42',
  ),
  14 => 
  array (
    'follower_userid' => '626',
  ),
  15 => 
  array (
    'follower_userid' => '655',
  ),
  16 => 
  array (
    'follower_userid' => '95',
  ),
)

根据如何在PHP中从多维数组中删除重复的值建议，我使用了$input = array_map("unserialize", array_unique(array_map("serialize", $input))); 执行array_unique()后的数组：

    array (
  0 => 
  array (
    'following_userid' => '88',
  ),
  1 => 
  array (
    'following_userid' => '89',
  ),
  2 => 
  array (
    'following_userid' => '287',
  ),
  3 => 
  array (
    'following_userid' => '346',
  ),
  4 => 
  array (
    'following_userid' => '405',
  ),
  5 => 
  array (
    'following_userid' => '284',
  ),
  6 => 
  array (
    'following_userid' => '583',
  ),
  7 => 
  array (
    'following_userid' => '587',
  ),
  8 => 
  array (
    'following_userid' => '655',
  ),
  9 => 
  array (
    'following_userid' => '95',
  ),
  10 => 
  array (
    'follower_userid' => '89',
  ),
  11 => 
  array (
    'follower_userid' => '88',
  ),
  12 => 
  array (
    'follower_userid' => '353',
  ),
  13 => 
  array (
    'follower_userid' => '42',
  ),
  14 => 
  array (
    'follower_userid' => '626',
  ),
  15 => 
  array (
    'follower_userid' => '655',
  ),
  16 => 
  array (
    'follower_userid' => '95',
  ),
)

但仍然得到了重复的答案。似乎对原始数组没有影响。

- Amit

Answer 1

首先，从5.2.9版本开始，您可以使用更简单的版本，取自this answer：

array_unique($array, SORT_REGULAR);

在这种情况下，array_unique()实际上给出了正确的输出；问题在于您的数组中有两个不同的键：“follower_userid”和“following_userid”，因此为了获得唯一的id而不考虑键，您必须先将其标准化：

array_map('current', $array);

做这件事情需要获取每个数组的第一个元素，并创建一个只包含这些第一个元素值的新数组。

输出：

Array
(
    [0] => 88
    [1] => 89
    [2] => 287
    [3] => 346
    [4] => 405
    [5] => 284
    [6] => 583
    [7] => 587
    [8] => 655
    [9] => 95
    [10] => 89
    [11] => 88
    [12] => 353
    [13] => 42
    [14] => 626
    [15] => 655
    [16] => 95
);

然后应用array_unique()：

array_unique(array_map('current', $array));

- Ja͢ck

Answer 2

如果它总是只有一个follower_userid，你可以使用以下方式将数组展平：

$followers = array();
foreach ($input as $item) {
    $followers[] = $item['followers_userid'];
}

$followers = array_unique($followers);

- duellsy