Multidimensional PHP array - Key exists

Question

I want a function that will return TRUE or FALSE based on if a given key exists in a multidimensional array in PHP.

I haven't been able to figure out a recursive function to perform this action.

A sample of what this could do:

$array = array(
    'key 1' => array(
        'key 1.1' => array()
        'key 1.2' => array()
    ),
    'key 2' => array(
        'key 2.1' => array(
            'key 2.1.1' => array()
        )
        'key 2.2' => array()
    )
);

multi_array_key_exists('key 1', $array); // return TRUE

multi_array_key_exists('key 2.1.1', $array); // return TRUE

multi_array_key_exists('key 3', $array); // return FALSE

Answer 1

This is where a recursive function comes in handy.

function multi_array_key_exists($key, array $array): bool
{
    if (array_key_exists($key, $array)) {
        return true;
    } else {
        foreach ($array as $nested) {
            if (is_array($nested) && multi_array_key_exists($key, $nested))
                return true;
        }
    }
    return false;
}

Note that this can take some time (in long nested arrays), it might be better to flatten first, since you are only interested in whether the key exists or not.

Answer 2

Maybe too late but here's a solution I came up with:

function multi_array_key_exists(array $path, array $array): bool
{
    if (empty($path)) {
        return false;
    }
    foreach ($path as $key) {
        if (isset($array[$key]) || array_key_exists($key, $array)) {
            $array = $array[$key];
            continue;
        }

        return false;
    }

    return true;
}

$testMe = ['my' => ['path' => ['exists' => true]]];
multi_array_key_exists(['my', 'path', 'exists'], $testMe);

I does not need costly recursive calls and is slightly faster (~15% on my setup).