How to check if an array has given keys

Question

From a performance perspective, what is the best way to check whether an associated array has and only has a given set of keys? Same question, but from a code conciseness perspective?

function checkArrKeys(array $arr, array $keys):bool {
    $arrKeys=array_keys($arr);
    sort($arrKeys);
    sort($keys);
    return $arrKeys===$keys;
}

function checkArrKeys(array $arr, array $keys):bool {
    return ($cnt = count(array_intersect(array_keys($arr), $keys)))===count($arr) && $cnt===count($keys);
}

function checkArrKeys(array $arr, array $keys):bool {
    return !(array_diff_key($arr, array_flip($keys)) || array_diff_key(array_flip($keys), $arr));
}

Andreas · Answer 1 · 2019-06-16T15:30:41.873

0

Not sure about the performance but this is one way.
Merge the keys with the array_keys and count the values.
Then remove all that had the value 2, if something is left there is a difference.

$merged = array_diff(array_count_values(array_merge($keys, array_keys($arr))), [2]);

https://3v4l.org/ATSHF

edited Jun 16 '19 at 15:30

answered Jun 16 '19 at 14:47

Andreas

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Thanks Andreas. This doesn't ensure extra keys are passed in `$arr`. – user1032531 Jun 16 '19 at 15:19
Found myself doing this differently each time, and want to settle on one approach and stick with it. – user1032531 Jun 16 '19 at 15:23
Definitely didn't think of that one! :) – user1032531 Jun 16 '19 at 15:35

Sudipto Chowdhury · Answer 2 · 2019-06-16T15:11:37.443

0

You can do this simply, by

 function ArrayKeysAreEqual(array $keys, array $arr)
 {
    return array_diff(array_keys($arr), $keys) === array_diff($keys, array_keys($arr)); // return true if matches
 }

edited Jun 16 '19 at 15:11

answered Jun 16 '19 at 14:55

Sudipto Chowdhury

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3

Thanks. Agree it will work, but will be the same as returning true if both are empty. – user1032531 Jun 16 '19 at 15:26
yeah, it will return true if both arrays are empty. – Sudipto Chowdhury Jun 17 '19 at 05:13

nice_dev · Answer 3 · 2019-06-16T15:30:53.967

0

You could use array_diff() on this with a count() check.

function checkArrKeys(array $arr, array $keys):bool {
    return count(array_diff(array_keys($arr),$keys)) === 0 && count($keys) === count(array_keys($arr));
}

edited Jun 16 '19 at 15:30

answered Jun 16 '19 at 15:07

nice_dev

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Thanks vivek_23, but don't think this will ensure that all the keys are passed. – user1032531 Jun 16 '19 at 15:22
@user1032531 Didn't get what you mean. Any example? – nice_dev Jun 16 '19 at 15:23
1

What if `$keys` has elements which are not in `$arr`? Per the docs: Compares array1 against one or more other arrays and returns the values in array1 that are not present in any of the other arrays. – user1032531 Jun 16 '19 at 15:25
@user1032531 Fixed it. I initially overlooked that as the naming convention is a bit misleading. – nice_dev Jun 16 '19 at 15:31
1

Ah, better. Similar to my middle example. I think I like yours more. – user1032531 Jun 16 '19 at 15:39
@user1032531 Great. If you want a fast algorithm performance wise, then you need to check on large arrays. – nice_dev Jun 16 '19 at 15:57

Martijn · Answer 4 · 2019-06-16T15:42:49.343

0

Just compare them:

function checkArrKeys(array $arr, array $keys):bool {
    $arrayKeys = array_keys($arr);
    sort($arrayKeys);

    return $arrayKeys === $keys; // 
}

$a = ['a'=>1, 'b'=>2, 'c'=>3, 'd'=>4];
$A = ['b'=>2, 'c'=>3, 'd'=>4, 'a'=>1];

$b = ['a'=>1, 'b'=>2, 'c'=>3];
$c = ['a'=>1, 'b'=>2, 'c'=>3, 'd'=>4, 'e'=>5];


$keys = ['a','b','c', 'd'];
var_dump(array_keys($a)===$keys); // true
var_dump(array_keys($A)===$keys); // false
var_dump(array_keys($b)===$keys);  // false
var_dump(array_keys($c)===$keys);  // false

function checkArrKeys(array $arr, array $keys):bool {
    $arrayKeys = array_keys($arr);
    sort($arrayKeys);

    return $arrayKeys === $keys; // 
}
echo "\n";

var_dump(checkArrKeys($a, $keys)); // true
var_dump(checkArrKeys($A, $keys)); // true
var_dump(checkArrKeys($b, $keys)); // false
var_dump(checkArrKeys($c, $keys)); // false

Try it online

edited Jun 16 '19 at 15:42

answered Jun 16 '19 at 15:36

Martijn

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I don't think it works. I originally planned on doing the same thing, but the indexes will be different and thus will not be equal. Hoping I am wrong because I think this is definitely the most readable. – user1032531 Jun 16 '19 at 15:38
I've added examples which you can see online – Martijn Jun 16 '19 at 15:46
1

It works because they happen to be in the same order. Try changing `$keys` to `['c','b','a', 'd']` – user1032531 Jun 16 '19 at 15:53
Yes, which is why I have implemented `sort()` – Martijn Jun 16 '19 at 18:56

How to check if an array has given keys

4 Answers4