如何为关联数组创建索引数组

How to create an index array for an associative array?

本文关键字：数组创建索引关联 | 更新日期: 2023-09-27

$arr = [
2 => ["a", "b", "c"],
5 => ["j", "k", "l"],
9 => ["w", "x", "y", "z"]
];

为此，我想创建一个新的索引数组，如下所示：

$index = [
    "a" => 2,
    "b" => 2,
    "c" => 2,
    "j" => 5,
    "k" => 5,
    "l" => 5,
    "w" => 9,
    "x" => 9,
    "y" => 9,
    "z" => 9
]

我找不到任何PHP函数可以做到这一点，但我相信有一个。或者可能有一些已知的代码可以有效地做到这一点？

$index = array();
foreach ($arr as $k => $a) {
  foreach ($a as $v) {
    $index[$v] = $k;
  }
}