Narrowing occurred during type inference of ZEND_FETCH_DIM_W

[hikashop-nicolas]

Description

We're developing an ecommerce solution called HikaShop for the Joomla CMS. We've been at it for more than 10 years.
Several of our users report a warning happening when upgrading to PHP8 which says:
Warning: Narrowing occurred during type inference of ZEND_FETCH_DIM_W. Please file a bug report on bugs.php.net in /xxx/xxx/xxx/administrator/components/com_hikashop/helpers/helper.php on line 1381

You can read the reports here:
https://www.hikashop.com/forum/install-update/903846-update-hikashop-php.html

Unfortunately, we're not able to reproduce the warning on our end as it apparently only happens in some rare case. Also, it happens on a line which only has this:
include_once($include_file);

It's basically the main line of our main helper file to load all the other files (controllers, models, views, other helpers, etc). So the warning message doesn't help much. We could just add a @ to hide the warning, but since the message says to file a bug report, I'm doing that hoping someone has a better idea.

PHP Version

PHP 8

Operating System

No response

[kamil-tekiela]

Thanks for the report. Would it be possible to receive some more code context from around the line "helper.php on line 1381".
Is this file publicly available on GitHub? Can we see the file for ourselves and try to infer from the code which line could have triggered it?

[hikashop-nicolas]

Here is a zip of the helper.php file helper.zip

[kamil-tekiela]

@dstogov Would you be able to weigh in your opinion? Do we have enough information to narrow down the problem? I wasn't able to reproduce the issue with a clean installation of HikaShop on PHP 8.1.1, but I assume there are a lot of factors here.

[dstogov]

I can't reproduce the problem. The provided helper.php doesn't do any array updates at line 1381.

This warning is emitted during loading (compilation and optimization) of PHP file. It doesn't have to be executed.
Try to load this file using command line PHP interpreter, then find and separate the problematic function.

[hikashop-nicolas]

First, as a disclaimer, please note that I know nothing about the PHP engine itself. I use PHP but I don't know its inner workings.

What I understand from your message is that the error happens when a PHP file is required/included and something is wrong with the file being required/included. That's exactly what happens here since line 1381 has an include_once() call.
If what I understand is correct, then it means the warning message indicates the path of the file where the require/include is done but not the path of the file being required/included (where the actual problem is). And if so, improving that message in future versions of PHP would help understand why this is happening.

On a side note, one of the users reporting the issue to us mentioned during the weekend ( https://www.hikashop.com/forum/install-update/903846-update-hikashop-php.html#340449 ) that after updating to the latest version of HikaShop, he didn't had the warning anymore. So I suppose that message came from some code somewhere which wasn't compatible with PHP8, but that we've modified the code since then ( probably someone else reported an issue with a better message, on another environment ).

[dstogov]

I can't say what is wrong and fix this without a reproduction case. May be the warning message really mentions the incorrect file name.

[kamil-tekiela]

@hikashop-nicolas Could you get in contact with the user that reported this problem and get the file from their system. As you said, they might be using an older version of that file that has an array operation on that line. I saw that such an operation happens at least once in that file. I don't think it's an include; I think the file is correctly reported, but we are looking at a newer version that doesn't have this problem anymore. Also, it would be good to know the exact PHP version they are using.