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Date: Fri, 13 Jul 2018 16:48:29 -0600
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To: enno.woortmann@web.de
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Subject: Re: [PHP-DEV] [VOTE] array_key_first(), array_key_last(),
 array_value_first(), array_value_last()
From: levim@php.net (Levi Morrison)

On Mon, Jul 9, 2018 at 5:17 AM Woortmann, Enno <enno.woortmann@web.de> wrote:
>
> Hi,
>
> as the discussion got no new contributions I'd like to start the voting
> for the RFC fo add new functions for the handling of outer array elements.
>
> https://wiki.php.net/rfc/array_key_first_last
>
> To have a better separation I split up the vote for the functions. The
> first vote covers the functions to handle keys: array_key_first() and
> array_key_last(). The second vote covers the corresponding functions to
> handle the values: array_value_first() and array_value_last().
>
> As this RFC adds functions but doesn't change the language syntax a 50%
> + 1 majority is required for both votes. The votes are open until
> 2018-07-16.
>
> The discussion for this RFC is located at
>
> https://externals.io/message/102245
>
> Regards,
>
> Enno
>
>
>
>
> --
> PHP Internals - PHP Runtime Development Mailing List
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This entire time I felt like this should be possible in pure PHP.
Surely, somewhere, we have this capability already? I searched quite a
few functions but didn't find anything.

However, the feeling was right. Just moments ago Paul Crovella from
Stack Overflow mentioned to me that `array_slice` uses the terminology
`offset` to refer to the order of the entry rather than its key, so I
went looking. As far as I can tell from the [array_slice
implementation][1] it will not trigger copies and will be efficient if
using -1 to retrieve the last index. We can provide the parameter
`preserve_keys` an argument of true to get both the key and the value.
These functions *are* efficiently implementable in user-land!

Below is a proof-of-concept for the `array_offset` function [mentioned
by Nicolas Grekas][2] (which by the way, neither the RFC author nor
anyone else responded to this suggestion) that is simply a convenience
wrapper over `array_slice`:

    function array_offset(array $input, int $offset): ?array {
        $slice = array_slice($input, $offset, 1, true);
        return count($slice) ? $slice : null;
    }

    $assoc = ['one' => 1, 'two' => 2, 'three' => 3];
    $packd = range(1, 4);

    var_dump(array_offset($assoc, -1));
    var_dump(array_offset($packd, -1));

    var_dump(array_offset($assoc, 0));
    var_dump(array_offset($packd, 0));

Of course, the `array_slice` function can be used to build all of the
functions described in the RFC, as well.

My new opinion is that no new functions are required and that
improving the `array_slice` documentation is all that is necessary. It
currently does not show any examples of it working on associated
arrays, which is probably why none of us (many of us experts) realized
this through this discussion. This is especially true as "offset" in
some other situations really means "key", as in
`ArrayAccess::offsetGet`.

  [1]: https://github.com/php/php-src/blob/b9963969fd088dca6852483fdb1c6b7e1080764d/ext/standard/array.c#L3477-L3577
  [2]: https://externals.io/message/102245#102322