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To: "Pierre Joye" <pierre.php@gmail.com>, "Paul Dragoonis"
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Date: Mon, 14 May 2012 16:03:21 +0200
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Subject: Re: [PHP-DEV] [RFC] [DISCUSSION] array_part()
From: glopes@nebm.ist.utl.pt ("Gustavo Lopes")

On Mon, 14 May 2012 15:41:25 +0200, Paul Dragoonis <dragoonis@gmail.com>  
wrote:

> Gustavo, why would I use array_part() if I could use array_slice() to get
> the parts of an array between two offsets.
>

Obviously, if you want to do something that array_slice() already does,  
then you wouldn't have a lot of pressing reasons to use this instead. But  
this is not a very interesting question.

On the other hand, if you're asking what are differences between this and  
array_slice(), then:

* array_slice() only does slicing at the level 1 (it has no  
multidimensional slicing that would allow doing something like  
array_column(), see https://github.com/php/php-src/pull/56 )
* array_slice() only operates in an 'index-as-offset' mode, which is less  
efficient than 'index-as-key'. array_part() allows you to choose:

$arr = [-1 => 'a', 0 => 'b'];
array_slice($arr, 0, 1) // 'a'
array_slice($arr, -1, 1) // 'b'
array_part($arr, [0]) // 'a'
array_part($arr, [-1]) // 'b'
array_part($arr, [-1], true) // 'a'

* array_slice() has side-effects; it resets the internal array pointer.
* array_slice() can preserve keys, array_part() cannot because when  
collapsing levels this would mean the possibility of overwriting elements.

I'll improve the RFC with inline examples and this information later.

-- 
Gustavo Lopes