[PHP-DEV] [RFC] array_only() and array_except() – Utility functions for array key filtering

Muhammed_Arshid_KV · February 20, 2026, 9:25am

Hello Internals,

I would like to propose a new RFC titled array_only() and array_except().

RFC: https://wiki.php.net/rfc/array_only_except

This RFC proposes adding two utility functions to the PHP core:

• array_only(array $array, array $keys): array
• array_except(array $array, array $keys): array

These functions allow selecting or excluding specific keys from an array.

Similar helpers are commonly used in frameworks, and adding native support would improve readability and consistency in userland code.

Summary:

• array_only() returns a new array containing only the specified keys.
• array_except() returns a new array excluding the specified keys.
• Original array is not modified.
• Works with associative and numeric keys.
• No impact on SAPIs or on OPcache.

I would appreciate feedback and suggestions from the community.
If there is general agreement, I plan to move the RFC forward.

Thanks,
Muhammed Arshid KV

Claude_Pache · February 20, 2026, 10:08am

Le 20 févr. 2026 à 10:25, Muhammed Arshid KV arshidkv12@gmail.com a écrit :

Hello Internals,

I would like to propose a new RFC titled array_only() and array_except().

RFC: https://wiki.php.net/rfc/array_only_except

This RFC proposes adding two utility functions to the PHP core:

• array_only(array $array, array $keys): array
• array_except(array $array, array $keys): array

These functions allow selecting or excluding specific keys from an array.

Similar helpers are commonly used in frameworks, and adding native support would improve readability and consistency in userland code.

Summary:

• array_only() returns a new array containing only the specified keys.
• array_except() returns a new array excluding the specified keys.
• Original array is not modified.
• Works with associative and numeric keys.
• No impact on SAPIs or on OPcache.

I would appreciate feedback and suggestions from the community.
If there is general agreement, I plan to move the RFC forward.

Thanks,
Muhammed Arshid KV

Hi,

The principle of the RFC is interesting to me, as it is a situation I encounter from time to time. Two remarks:

It may be interesting to compare with currently available solutions. Currently, I use array_intersect_key and array_diff_key when I need the semantics of proposed array_only and array_except:

array_intersect_key($data, ['id' => null, 'email' => null]);

I think that the name of the new functions ought to make evident that we are filtering on keys and not on something else. I suggest: array_only_keys and array_except_keys.

—Claude

mickmackusa · February 20, 2026, 1:13pm

It seems clear to me that this proposal was under-researched because the RFC doesn’t even acknowledge the fact that PHP already has native functions which serve the exact same purpose (and they have more indicative names).

I’m not a voter, but I would vote No on this one because the new functions aren’t adding significant value to the language.

Mick

Muhammed_Arshid_KV · February 20, 2026, 5:37pm

Hi,

Thanks for the feedback.

Yes, array_intersect_key() and array_diff_key() can be used today, but the RFC proposes dedicated functions for better readability, less boilerplate, and potentially better performance and lower memory usage by avoiding temporary arrays.
Good point about naming. Making the key-filtering behavior explicit (e.g., array_only_keys and array_except_keys) improves clarity and avoids confusion.

On Fri, 20 Feb 2026, 3:38 pm Claude Pache, <claude.pache@gmail.com> wrote:

Le 20 févr. 2026 à 10:25, Muhammed Arshid KV <arshidkv12@gmail.com> a écrit :

Hello Internals,

I would like to propose a new RFC titled array_only() and array_except().

RFC: https://wiki.php.net/rfc/array_only_except

This RFC proposes adding two utility functions to the PHP core:

• array_only(array $array, array $keys): array
• array_except(array $array, array $keys): array

These functions allow selecting or excluding specific keys from an array.

Similar helpers are commonly used in frameworks, and adding native support would improve readability and consistency in userland code.

Summary:

• array_only() returns a new array containing only the specified keys.
• array_except() returns a new array excluding the specified keys.
• Original array is not modified.
• Works with associative and numeric keys.
• No impact on SAPIs or on OPcache.

I would appreciate feedback and suggestions from the community.
If there is general agreement, I plan to move the RFC forward.

Thanks,
Muhammed Arshid KV

Hi,

The principle of the RFC is interesting to me, as it is a situation I encounter from time to time. Two remarks:

It may be interesting to compare with currently available solutions. Currently, I use array_intersect_key and array_diff_key when I need the semantics of proposed array_only and array_except:
array_intersect_key($data, ['id' => null, 'email' => null]);
I think that the name of the new functions ought to make evident that we are filtering on keys and not on something else. I suggest: array_only_keys and array_except_keys.

—Claude

Tim_Dusterhus · February 22, 2026, 6:25pm

Hi

The same comments as with your other RFC apply here.

On 2/20/26 18:37, Muhammed Arshid KV wrote:

1. Yes, *array_intersect_key() *and *array_diff_key() *can be used today,
but the RFC proposes dedicated functions for better readability, less
boilerplate, and potentially better performance and lower memory usage by
avoiding temporary arrays.

Can you elaborate on what you mean by “lower memory usage by avoiding temporary arrays”?

2. Good point about naming. Making the key-filtering behavior explicit
(e.g., *array_only_keys* and *array_except_keys*) improves clarity and
avoids confusion.

I don't think that `array_(only|except)_keys()` is particularly clear. From the naming I would expect it to return the array keys / values (i.e. do the same as `array_keys()` and `array_values()` respectively).

Best regards
Tim Düsterhus

Muhammed_Arshid_KV · February 22, 2026, 6:58pm

Hi,

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.

In a native C implementation, we can iterate over $keys and copy values directly into the result without creating that temporary array. That means fewer allocations and lower peak memory usage, especially with large key sets or inside loops.

Thanks.

On Sun, 22 Feb 2026, 11:55 pm Tim Düsterhus, <tim@bastelstu.be> wrote:

Hi

The same comments as with your other RFC apply here.

On 2/20/26 18:37, Muhammed Arshid KV wrote:

Yes, *array_intersect_key() *and *array_diff_key() *can be used today,
but the RFC proposes dedicated functions for better readability, less
boilerplate, and potentially better performance and lower memory usage by
avoiding temporary arrays.

Can you elaborate on what you mean by “lower memory usage by avoiding
temporary arrays”?

Good point about naming. Making the key-filtering behavior explicit
(e.g., array_only_keys and array_except_keys) improves clarity and
avoids confusion.

I don’t think that array_(only|except)_keys() is particularly clear.
From the naming I would expect it to return the array keys / values
(i.e. do the same as array_keys() and array_values() respectively).

Best regards
Tim Düsterhus

Tim_Dusterhus · March 1, 2026, 2:10pm

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 PHP: rfc.

Muhammed_Arshid_KV · March 1, 2026, 2:22pm

Hi Tim,

Thanks for the explanation.

In this example,

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

the second argument is an associative array.

But in my array_only(array $input, array $keys) function, $keys is a numeric array. Working with a numeric array may be slightly faster than building an associative array first.

Just wanted to clarify that point.

Best regards,

Muhammed Arshid KV

On Sun, 1 Mar 2026, 7:40 pm Tim Düsterhus, <tim@bastelstu.be> wrote:

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.

Muhammed_Arshid_KV · March 5, 2026, 5:23am

Hi,

I think the RFC “array_only_except” is ready to move to the voting phase.

If there are no further objections or required changes, I would like to proceed with starting the vote.

Thanks.