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Date: Mon, 4 Jan 2016 18:50:32 +0000
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Subject: Re: [PHP-DEV] Re: [RFC] array_key_(first|last|index) functions
 proposal
From: rowan.collins@gmail.com (Rowan Collins)

On 04/01/2016 17:05, Andrea Faulds wrote:
> How often would such functions be useful? Perhaps they fill a gap, but 
> I'm not sure if it's one that needs filling. array_key_first and 
> array_key_last can already be accomplished in two or so lines of code 
> (four if you make a function), and array_key_index can be implemented 
> in a few lines with a foreach() loop and a counter.

Personally, I think they would be very handy, if accompanied by 
array_value_first and array_value_last. The "ordered hash" PHP provides 
is a very powerful structure, but sometimes you just want to peek at one 
or other end of the array without any side effects, and it feels weird 
that there's no neat idiomatic way of doing this.

Incidentally, the ability to define the functions in userland is quite a 
positive - it means they can be polyfilled and codebases can start 
making use of them without requiring a major version bump.


> array_key_first and array_key_last seem mostly harmless, at least. I'm 
> not sure the same can be said for array_key_index, since it has O(n) 
> complexity. [...] I would rather we not include this specific 
> function, and avoid potentially disguising the time complexity of key 
> lookup, especially as I can't think of a good use-case for it.

This argument does seem reasonable - I can't think of many situations 
where you'd want exactly one key or element, at a known position, in an 
indexed array. And as soon as you want two keys or elements, you're 
probably better off using array_keys / array_values to give you a list 
which can be efficiently randomly accessed.

Regards,

-- 
Rowan Collins
[IMSoP]