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Date: Sun, 19 Sep 2021 08:44:09 -0500
To: "php internals" <internals@lists.php.net>
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Subject: =?UTF-8?Q?Re:_[PHP-DEV]_Proposal:_Adding_an_ARRAY=5FFILTER=5FREINDEX_fla?=
 =?UTF-8?Q?g_to_array=5Fvalues?=
From: larry@garfieldtech.com ("Larry Garfield")

On Sun, Sep 19, 2021, at 8:11 AM, tyson andre wrote:
> Hi internals,
> 
> Currently, array_filter will always return the original keys.
> This often requires an additional wrapping call of 
> array_values(array_filter(...)) to reindex the keys and return a list.
> (or applications may not realize there will be gaps in the keys until 
> it causes a bug or unexpected JSON encoding, etc.)
> 
> PHP is also more memory/time efficient at creating packed arrays than 
> it is at creating associative arrays.
> 
> What are your thoughts on adding `ARRAY_FILTER_REINDEX`, to ignore the 
> original int/string keys and replace them with `0, 1, 2, ...`
> 
> ```
> php > echo json_encode(array_filter([5,6,7,8], fn($value) => $value % 2 
> > 0));
> {"0":5,"2":7}
> // proposed flag
> php > echo json_encode(array_filter([5,6,7,8], fn($value) => $value % 2 
> > 0, ARRAY_FILTER_REINDEX));
> [5,7]
> ```
> 
> https://www.php.net/array_filter already has the `int $mode = 0` which 
> accepts the bit flags `ARRAY_FILTER_USE_KEY` and `ARRAY_FILTER_USE_BOTH`
> These could be then be combined with the proposed bit flag 
> `ARRAY_FILTER_REINDEX`, e.g. to filter an array based on both the array 
> keys and values, and return a list without gaps.
> (and if $callback is null, this would return a list containing only the 
> truthy values)
> 
> Thoughts? 
> 
> Thanks,
> Tyson

In cases where I do want it reindexed, the existing array_values() is fine in most cases.  Creating small, purpose-built tools that are easily composed is generally the right strategy.  The only time I could see a flag being a better alternative is when the memory difference would be huge.  Do we have a sense for how much of a memory difference we'd be looking at by combining it into a single operation?

(There's also the grossness of nesting functions inside each other, but the answer to that is pipes, not more flags.)

--Larry Garfield