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Subject: Re: [PHP-DEV] RFC - Array slice syntactic sugar
From: larry@garfieldtech.com (Larry Garfield)

On 3/19/15 3:49 PM, Alex Bowers wrote:
> This email is just to gauge the response for some syntactic sugar to be
> added to PHP in regard to slicing an array.
>
> My proposal is something similar to Pythons slice, in PHP this would look
> like:
>
> $slided = $array[1:4]
>
> This will get the elements in positions 1,2,3,4. (1 through 4 inclusive),
> ignoring the actual key of the array. The result for an array will be an
> array with the keys preserved, in the same order. Any multi-dimensions are
> also respected and returned within the array.
>
> This is the same as using the array_slice method with the PRESERVE KEYS
> fourth parameter passed through as true.
>
> The result for a string is the string from the two positions indicated.
> This is the same as using substr().
>
> The benefits for this as I see it is:
>
> 1) No function overhead
> 2) More readable (opinionated)
> 3) Consistent with how we can select items from an array currently (using
> index).
>
> If the array is not long enough (for example, index 4 doesn't exist), then
> a NOTICE is thrown, and the values returned are as much as possible; this
> would be the same as calling $array[1:] which will get the items in
> position 1 through to the end.
>
> If the variable used contains a string, then this will get the values from
> the string at those positions. The same way that $string[1] will get the
> second character, $string[2:5] will get the third through to the sixth
> character. This differs from array_slice which would throw a warning and
> return null.
>
> If the variable isn't either a string or an array (or convertible to
> either); then a warning is thrown and null is returned, consistent with
> current use ($int[0] will return null)
>
> Arrays with associated keys cannot be selected by using the keys they have,
> but instead should be selected by the position those keys hold.
>
> For example, this is invalid:
>
> $array['string':'end']. This should throw a fatal error.
>
> The valid options are:
>
> $array[from:to] - This gets the values from position 'from' to 'to'
> inclusive
> $array[from:] - This gets the values from the position 'from' to the end.
> $array[:to] - This gets the values from the start to the position 'to'.
>
> $array[:] will get all the items in the array ($same as doing $array)
>
> A side addition, that may be considered is adding [-1] to get the last item
> in the array. But that is not a main part of this RFC.
>
> Thanks


Variations of this proposal have been discussed many times.  I don't 
recall what the pushback was but it's worth your time to check the 
archives to see what the objections were and if you can address them, 
and/or if the new engine in PHP 7 addresses them.  (I suspect it 
has/will ameliorate a lot of implementation-level issues with old 
proposals.)

Personally I'd be in favor of such a syntax but I don't recall the 
objections in the past beyond "meh, sugar".

--Larry Garfield