Re: [RFC] array_only() and a rray_except() – Utility functions for array key f iltering

Hi Am 2026-02-22 19:58, schrieb Muhammed Arshid KV:

Here is a simple example of an array_only() implementation using existing PHP functions:

function array_only(array $input, array $keys): array {
    return array_intersect_key($input, array_flip($keys));
}

This works, but array_flip($keys) creates an extra temporary hash table. So peak memory becomes: input + keys + flipped array + result.

That is true for this specific implementation of a “wrapper function”. It is not necessarily true for other implementations, e.g. simply using the functions directly instead of creating a wrapper for two method calls. array_flip() supports compile-time evaluation, so you can just write:

    $dataWithOnlyIdAndEmail = \array_intersect_key($data, \array_flip(['id', 'email']));

and OPcache will make sure to rewrite it to:

    $dataWithOnlyIdAndEmail = \array_intersect_key($data, ['id' => 0, 'email' => 1]);

avoiding the intermediate array. Best regards Tim Düsterhus PS: It appears that the RFC is not listed in the overview at https://wiki.php.net/rfc.