CODEWITHSUNDEEP
phparrays
Roy
Roy

Reputation: 987

How to create an index array for an associative array?

I have this multidimensional array:

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

For which I'd like to create a new index array like this one:

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

I couldn't find any PHP function that appears to do that, but I'm sure there is one. Or maybe there's some known code that does this efficiently?

Upvotes: 0

Views: 50

Answers (1)

CrayonViolent
CrayonViolent

Reputation: 32517

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

Upvotes: 4

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