mb_str_split false return

[GrahamCampbell]

Bug report

mb_str_split split may return false on error, but PHPStan no longer thinks so (but it used to not complain about this). For example, on PHP 7.4: https://3v4l.org/9ZQGj.

Code snippet that reproduces the problem

https://phpstan.org/r/e5baddbc-759f-426b-aa23-7e0a23cf25a8

Expected output

No issue.

[ThomasLandauer]

I was just about to report the same, and already had the playground prepared :-)
https://phpstan.org/r/8b1844d5-06c0-45c5-847c-3b1c3474b448

I think the problem is coming from phpstan/phpstan-src#379

https://www.php.net/manual/en/function.mb-str-split.php#refsect1-function.mb-str-split-returnvalues says:

mb_str_split() returns an array of strings, or FALSE on failure.

[ondrejmirtes]

Turns out str_split and mb_str_split are not exactly the same. /cc @VincentLanglet.

[VincentLanglet]

I was just about to report the same, and already had the playground prepared :-)
https://phpstan.org/r/8b1844d5-06c0-45c5-847c-3b1c3474b448

Phpstan is correctly returning an error, since the value is ['a', 'b', 'c'] and will never be false.

mb_str_split() returns an array of strings, or FALSE on failure.

Yes, but like str_split, their are some case where we can be sure that it won't return false.

Turns out str_split and mb_str_split are not exactly the same. /cc @VincentLanglet.

I would say that when mb_str_split is used with exactly 2 parameters, it behave exactly like str_split.

If the third parameter is a contant

• if it's a valid encoding, it behave like str_split.
• if it's an invalid encoding, it's always false.
  Related to https://www.php.net/manual/fr/mbstring.supported-encodings.php

If the third parameter is a variable, we can't know.

It's maybe easier to use a different FunctionReturnType extension for str_split and for mb_str_split.
But as a quick fix of mb_str_split, it could behave like str_split only if the third parameter is omitted. WDYT ?

[ondrejmirtes]

We can change the returned type for mb_str_split based on the third argument.

There's already some extension in PHPStan itself that checks this function (mb_list_encodings), feel free to draw inspiration from that.

[VincentLanglet]

Will try something phpstan/phpstan-src#396

[ondrejmirtes]

Fixed by: phpstan/phpstan-src#396

[github-actions]

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