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

Where are your attempts at writing multi_array_key_exists? — Izkata
– Izkata, Commented Nov 14, 2013 at 19:06

kero · Accepted Answer · 2019-10-29 15:16:14Z

7

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.

edited Oct 29, 2019 at 15:16

answered Nov 14, 2013 at 19:06

kero

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Comments

xlttj · Accepted Answer · 2021-02-25 17:05:56Z

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).

edited Feb 25, 2021 at 17:05

answered Feb 25, 2021 at 16:52

xlttj

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1 Comment

Mac Over a year ago

It's never too late for a useful solution! 👍

Tourist · Accepted Answer · 2022-08-28 14:37:48Z

If you want to find the endpoint key [Knowing only the last key] (But that key could exist in multiple sub elements)

    public function has(array $array, string $pointer): bool
    {
        $iterator = new RecursiveIteratorIterator(
            new RecursiveArrayIterator($array), 
            RecursiveIteratorIterator::SELF_FIRST
        );

        foreach($iterator as $key => $value){
            if($key === $pointer) {
                return true;
            }
        }

        return false;
    }

If you want to to check a key in a sequence like... users.admins.is_big_boss

    public function has(array $array, string $pointer): bool
    {
        $depth = explode('.', $pointer);
        $base = $array;

        for($i=0; $i < count($depth); $i++) {

            if(!isset($base[$depth[$i]])) {
                return false;
            }

            $base = $base[$depth[$i]];
        }

        return true;
    }

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