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[RFC] Consistent null behaviour

php.internals

Ilija Tovilo

8 years ago

Hi everybody!

To my surprise, I noticed today that an array access on a `null` value returns `null` without any warning whatsoever.
Accessing the property of a `null` value gives you a notice, while calling a function on that `null` value gives you a fatal error.

https://3v4l.org/ZSZHN

This is pretty inconsistent. IMO all of these should be fatal errors, although I realize that might be a bit drastic for PHP 8.
We should at least give the user a notice when using array access on a `null` value.

Any thoughts?

Regards,
Ilija

lists@rhsoft.net

8 years ago

Am 20.09.2017 um 19:06 schrieb ilija.tovilo@me.com:

> Hi everybody!
>
> To my surprise, I noticed today that an array access on a `null` value returns `null` without any warning whatsoever.
> Accessing the property of a `null` value gives you a notice, while calling a function on that `null` value gives you a fatal error.
>
> https://3v4l.org/ZSZHN
>
> This is pretty inconsistent. IMO all of these should be fatal errors, although I realize that might be a bit drastic for PHP 8.
> We should at least give the user a notice when using array access on a `null` value.
>
> Any thoughts?

wouldn't that break code like below which is IMHO the best usecase of
the PHP 5.6 feature that you can directly access a array field of a
function result and the type-casting encsues that the return-type is
always int

function GetSKatMaxSort(int $archive=0): int
{
return (int)mysqli_fetch_row($this->db->query("select SQL_NO_CACHE
max(ssort) from {$this->db->table} where sarchive=$archive", 1))[0];
}

Ilija Tovilo

8 years ago

I realized after sending the initial E-Mail that there might be more breaking changes than I thought, like the one you suggested.

The same thing actually happens for bools, ints and floats:
https://3v4l.org/jvVbO

I wouldn’t depend on this behaviour since you’d get errors depending on what is returned, like an empty array, a string, an object or resource.

Regards

On 20 Sep 2017, 19:18 +0200, lists@rhsoft.net <lists@rhsoft.net>, wrote:

lists@rhsoft.net

8 years ago

Am 20.09.2017 um 19:23 schrieb ilija.tovilo@me.com:

> I realized after sending the initial E-Mail that there might be more
> breaking changes than I thought, like the one you suggested.
>
> The same thing actually happens for bools, ints and floats:
> https://3v4l.org/jvVbO
>
> I wouldn’t depend on this behaviour since you’d get errors depending on
> what is returned, like an empty array, a string, an object or resource.

i would depend on that behavior because in reality you can get back two
different things:

* a numeric array with exactly index 0
* NULL

how do you imagine mysqli_fetch_row() return empty array, string or even
object/resource? when nothing is found it's a non-empty array and
otherwise NULL

before PHP 5.6 (or PHP 5.5 not sure) these where useless multiple lines
because you needed to store the result of mysqli_fetch_row() in some var
to access key 0

Christoph Becker

8 years ago

On 20.09.2017 at 19:06, ilija.tovilo@me.com wrote:

> To my surprise, I noticed today that an array access on a `null` value returns `null` without any warning whatsoever.
> Accessing the property of a `null` value gives you a notice, while calling a function on that `null` value gives you a fatal error.
>
> https://3v4l.org/ZSZHN
>
> This is pretty inconsistent. IMO all of these should be fatal errors, although I realize that might be a bit drastic for PHP 8.
> We should at least give the user a notice when using array access on a `null` value.

There is already a respective RFC[1] which has been accepted for PHP
7.2, but there are issues[2].

[1] <https://wiki.php.net/rfc/notice-for-non-valid-array-container>
[2] <http://news.php.net/php.internals/97520>

--
Christoph M. Becker