Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:130130
Precedence: list
MIME-Version: 1.0
References: <CAO3baw=Qe-w4UOQzc4_NO=b41N-DJtf8U9Q6HybMCcCtZoEqgA@mail.gmail.com>
 <3ACF2D3E-0376-4033-8CAA-84FAD83E2A69@gmail.com> <CAO3baw=A5hnGCWbY3_4LE=nYm8+=R1kcAvfjKQWLS-ODyXx0Kw@mail.gmail.com>
 <f0891adc-f114-4217-9ac9-1692d8226f8c@bastelstu.be>
In-Reply-To: <f0891adc-f114-4217-9ac9-1692d8226f8c@bastelstu.be>
Date: Mon, 23 Feb 2026 00:28:59 +0530
Message-ID: <CAO3bawnw7WvNT=1PDa0rw+S5_5aKnM6kYSOdL=zY8kpXwtV6eQ@mail.gmail.com>
Subject: =?UTF-8?Q?Re=3A_=5BPHP=2DDEV=5D_=5BRFC=5D_array=5Fonly=28=29_and_array=5Fexcept=28=29_?=
	=?UTF-8?Q?=E2=80=93_Utility_functions_for_array_key_filtering?=
To: =?UTF-8?Q?Tim_D=C3=BCsterhus?= <tim@bastelstu.be>
Cc: Claude Pache <claude.pache@gmail.com>, internals@lists.php.net
Content-Type: multipart/alternative; boundary="000000000000e04bf3064b6e3f96"
From: arshidkv12@gmail.com (Muhammed Arshid KV)

--000000000000e04bf3064b6e3f96
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

Hi,

Here is a simple example of an `array_only()` implementation using existing
PHP functions:

```php
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=E2=80=AFpm Tim D=C3=BCsterhus, <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:
> > 1. Yes, *array_intersect_key() *and *array_diff_key() *can be used toda=
y,
> > 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 =E2=80=9Clower memory usage by avoi=
ding
> temporary arrays=E2=80=9D?
>
> > 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 D=C3=BCsterhus
>

--000000000000e04bf3064b6e3f96
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"auto">Hi,<div dir=3D"auto"><br></div><div dir=3D"auto">Here is =
a simple example of an `array_only()` implementation using existing PHP fun=
ctions:</div><div dir=3D"auto"><br></div><div dir=3D"auto">```php</div><div=
 dir=3D"auto">function array_only(array $input, array $keys): array {</div>=
<div dir=3D"auto">=C2=A0 =C2=A0 return array_intersect_key($input, array_fl=
ip($keys));</div><div dir=3D"auto">}</div><div dir=3D"auto">```</div><div d=
ir=3D"auto"><br></div><div dir=3D"auto">This works, but `array_flip($keys)`=
 creates an extra temporary hash table.</div><div dir=3D"auto">So peak memo=
ry becomes: input + keys + flipped array + result.</div><div dir=3D"auto"><=
br></div><div dir=3D"auto">In a native C implementation, we can iterate ove=
r `$keys` and copy values directly into the result without creating that te=
mporary array. That means fewer allocations and lower peak memory usage, es=
pecially with large key sets or inside loops.</div><div dir=3D"auto"><br></=
div><div dir=3D"auto">Thanks.</div><div dir=3D"auto"><br></div></div><br><d=
iv class=3D"gmail_quote gmail_quote_container"><div dir=3D"ltr" class=3D"gm=
ail_attr">On Sun, 22 Feb 2026, 11:55=E2=80=AFpm Tim D=C3=BCsterhus, &lt;<a =
href=3D"mailto:tim@bastelstu.be">tim@bastelstu.be</a>&gt; wrote:<br></div><=
blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px=
 #ccc solid;padding-left:1ex">Hi<br>
<br>
The same comments as with your other RFC apply here.<br>
<br>
On 2/20/26 18:37, Muhammed Arshid KV wrote:<br>
&gt; 1. Yes, *array_intersect_key() *and *array_diff_key() *can be used tod=
ay,<br>
&gt; but the RFC proposes dedicated functions for better readability, less<=
br>
&gt; boilerplate, and potentially better performance and lower memory usage=
 by<br>
&gt; avoiding temporary arrays.<br>
<br>
Can you elaborate on what you mean by =E2=80=9Clower memory usage by avoidi=
ng <br>
temporary arrays=E2=80=9D?<br>
<br>
&gt; 2. Good point about naming. Making the key-filtering behavior explicit=
<br>
&gt; (e.g., *array_only_keys* and *array_except_keys*) improves clarity and=
<br>
&gt; avoids confusion.<br>
<br>
I don&#39;t think that `array_(only|except)_keys()` is particularly clear. =
<br>
=C2=A0From the naming I would expect it to return the array keys / values <=
br>
(i.e. do the same as `array_keys()` and `array_values()` respectively).<br>
<br>
Best regards<br>
Tim D=C3=BCsterhus<br>
</blockquote></div>

--000000000000e04bf3064b6e3f96--