php array_intersect associative and indexed array - php

Question

How can I check if keys are set in an array without using multiple isset(...)
I thought of something like:
$arr1 = [
"keyA" => 1,
"keyB" => 2,
"keyC" => 3
];
$arr2 = ['keyB', 'keyD'];
$anyExists = empty(array_intersect($arr1, $arr2));
This should evaluate to true if any item of $arr2 is a key of $arr1.
It obviously does not work. But is there a similarly nice solution without using loops?

Answer 1

So you want to get the keys as values from the first array as it checks values and not keys, and you want !empty() to return true if it's NOT empty and false if it IS empty:
$anyExists = !empty(array_intersect(array_keys($arr1), $arr2));
You could use array_intersect_key(), but then you would need to flip the second array to get the values as keys:
$anyExists = !empty(array_intersect_key($arr1, array_flip($arr2)));
Or define your array as:
$arr2 = ['keyB' => true, 'keyD' => true];

Answer 2

I find disallowing multiple isset() calls to be an unfortunate requirement because it is sure to be the faster option. Additionally, by writing the calls into a loop with a conditional break or return will improve its efficiency again.
Code: (Demo)
function anyKeyExists($haystack, $needles) {
foreach ($needles as $needle) {
if (isset($haystack[$needle])) {
return true;
}
}
return false;
}
$array = [
"keyA" => 1,
"keyB" => 2,
"keyC" => 3
];
echo "noMatch: " , (int)anyKeyExists($array, ['keyD', 'keyF']) , "\n";
echo "oneMatch: " , anyKeyExists($array, ['keyB', 'keyD']) , "\n";
echo "twoMatches: " , anyKeyExists($array, ['keyA', 'keyC']) , "\n";
Output:
noMatch: 0
oneMatch: 1
twoMatches: 1
If you must use functional programming, you can avoid the empty() call after intersecting the keys by merely casting the output array as a boolean using !! or (bool).
Code: (Demo)
$array = [
"keyA" => 1,
"keyB" => 2,
"keyC" => 3
];
echo "noMatch: " , (int)!!array_intersect_key($array, array_flip(['keyD', 'keyF'])) , "\n";
echo "oneMatch: " , !!array_intersect_key($array, array_flip( ['keyB', 'keyD'])) , "\n";
echo "twoMatches: " , !!array_intersect_key($array, array_flip(['keyA', 'keyC'])) , "\n";
(Same output as previous snippet)
P.s. It should be obvious, but in case it is not, I'll explain that my techniques are returning true or false evaluations. I am casting the false outcomes as (int) so that they are expressed as 0 values instead of empty strings. true, when echoed, is represented as a 1.