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Date: Wed, 1 Aug 2018 15:59:30 -0400
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To: Marcos Passos <marcospassos.com@gmail.com>
Cc: internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Array max size
From: pollita@php.net (Sara Golemon)

On Wed, Aug 1, 2018 at 2:41 PM, Marcos Passos
<marcospassos.com@gmail.com> wrote:
> Whenever you look for more information about the maximum size of an array,
> you find someone saying that "PHP arrays do not have a maximum size, but
> the amount of memory available". However, I could not find any excerpt in
> PHP documentation that supports that.
>
I would say that *AS A LANGUAGE*, PHP does in fact have no limit on
array sizes. Period.

Beyond that definition in the language specification, there come two
limiting factors:

1. The hardware limitation of the machine running PHP.  i.e. How much
memory it has.  This is the most practical answer for most users.

2. Implementation details of the PHP runtime.  The reference
implementation of PHP uses a uint32_t to keep track of the number of
elements for quick and easy O(1) access.  This may or may not limit
the array to (2^32-1) elements, but it does certainly limit the
functionality of count() when operating on arrays.  I think
documenting in the php.net manual (which refers solely to the
reference implementation) a limit of (2^32-1) elements as an
implementation detail is not unreasonable, but it's worthy of nothing
more than a footnote on the arrays reference page.  The answer in #1
about memory limits is FAR more salient to typical uses.

-Sara