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Date: Wed, 1 Aug 2018 16:44:54 -0300
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To: Sherif Ramadan <theanomaly.is@gmail.com>
Cc: PHP Internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Array max size
From: marcospassos.com@gmail.com (Marcos Passos)

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It looks like the limit I mentioned, used by some functions, is
architecture-dependent:
https://github.com/php/php-src/blob/master/Zend/zend_types.h#L288

Also, that's such a ridiculously large number for the vast majority of
> people using PHP that hardly anyone ever runs into this limit.


The point is not about the possibility of crossing the limit of the array,
but the need for a definition is one to design a method or function whose
behavior aligns with the array capabilities. This need, in fact, became
more noticeable from a design point of view since the introduction of the
iterable pseudo-type.

No one ever said "this is what will happen if a PHP array exceeds <this>
> size". Until someone does that, I cannot document it.


I cannot disagree more with this statement.

- Marcos

2018-08-01 16:29 GMT-03:00 Sherif Ramadan <theanomaly.is@gmail.com>:

> It's undocumented, because it's considered undefined behavior. PHP arrays
> implicitly store the number of elements internally as an unsigned 32 bit
> integer (regardless of architecture). This means that (technically) you
> can't create an array with more than ((2**31) - 1) elements (or
> 2,147,483,647 elements). However, PHP won't actually attempt to stop you
> from doing this! The problem is, once you exceed these number of elements,
> the integer will overflow, causing undefined behavior (all kinds weird
> bugs). So we cannot document behavior that was never defined. No one ever
> said "this is what will happen if a PHP array exceeds <this> size". Until
> someone does that, I cannot document it. Also, that's such a ridiculously
> large number for the vast majority of people using PHP that hardly anyone
> ever runs into this limit.
>
>
>
>
> On Wed, Aug 1, 2018 at 2:42 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.
>>
>> Even if the engine imposes no hard limit on the size of an array, in fact,
>> there an inherent limit that is assumed by some functions, and that is
>> what
>> I would like to suggest making explicit on the documentation. The lack of
>> this definition leads to inconsistencies and leaves several open
>> questions,
>> including:
>>
>>    - If no limit exists, then it's conceptually possible to have an array
>>    with *PHP_INT_MAX + 1* elements. In that sense, what would be the
>> return
>>    of the *\count()*?
>>    - The function *range* validates the size of the resulting range
>> against
>>    the maximum size of the hash table (defined internally as
>> *HT_MAX_SIZE*),
>>    and throw an error if it exceeds that value. Is that the limit?
>>    - he function *array_fill*, in contrast, does not rely on *HT_MAX_SIZE*
>>    for validating the size of the result. But, why?
>>    - The documentation says that omitting the third parameter of
>>    array_split is equivalent to \count($array). If the maximum number
>>    representable in PHP is *PHP_INT_MAX*, is the max size the same as
>>    *PHP_INT_MAX*?
>>
>> There are other examples, but I think these are enough to make the point.
>>
>> My understanding is that the conceptual limit is *PHP_INT_MAX*, as there
>> is
>> no way to represent the size above this value. If so, the interval that
>> represents all possibles indexes for an array is defined as *0 <= index <=
>> PHP_INT_MAX -1*. That definition aligns with all functions that support
>> negative length as *-PHP_INT_MAX* is equivalent to the start of the array.
>>
>> Could you guys please share your thoughts on this topic?
>>
>

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