如何使用所有索引值制作单个数组？ [重复]

Question

This question already has an answer here:

• Get keys from multidimensional array recursively 2 answers

Array
(
    [8] => Array
        (
            [9] => Array
                (
                    [13] => Array()
            )
    )

[14] => Array
    (
        [15] => Array()
    )
)

I want all index value in single array like this one array('8','9','13','14','15');

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Answer 1

You could combine the array_keys() function with recursion to grab all keys inside your array like shown below:

// Your given array
$array = [
    8 => [
        9 => [
            13 => []
        ]
    ],

    14 => [
        15 => []
    ]
];

// What this function does, is it loops through the array, and if the given
// value is an array too, it does the same until it hits a value which is not an array
function array_keys_recursive($array, $keys = []) {
    foreach ($array as $key => $value) {
        $keys[] = $key;

        if (is_array($value)) {
            $keys = array_merge($keys, array_keys_recursive($value));
        }
    }

    return $keys;
}

// You call it like a so:
$keys = array_keys_recursive($array);
print_r($keys); // Outputs Array ( [0] => 8 [1] => 9 [2] => 13 [3] => 14  [4] => 15 )