Add support for PHP 8.1

[paulbalandan]

Description:
PHP 8.1 will be released in a few months and we should ensure the framework is compatible by then.

Detected issues:

• Declaration of CodeIgniter\Session\Handlers\ArrayHandler::gc($maxlifetime): bool should be compatible with SessionHandlerInterface::gc(int $max_lifetime): int|false (Fixed in Make the session handlers all compatible with SessionHandlerInterface #5012)
• FILTER_SANITIZE_STRING is deprecated Bug: FILTER_SANITIZE_STRING is deprecated (PHP 8.1.0 early test) #4938 (Fixed in Replace deprecated FILTER_SANITIZE_STRING #5005 and Replace usage of FILTER_SANITIZE_STRING #5263)
• During inheritance of ArrayAccess: Uncaught Return type of CodeIgniter\Cookie\Cookie::offsetExists($offset) should either be compatible with ArrayAccess::offsetExists(mixed $offset): bool, or the #[ReturnTypeWillChange] attribute should be used to temporarily suppress the notice (Fixed in Make Cookie compatible with ArrayAccess #5004)
• Fatal error: During inheritance of IteratorAggregate: Uncaught Return type of CodeIgniter\Cookie\CookieStore::getIterator() should either be compatible with IteratorAggregate::getIterator(): Traversable, or the #[ReturnTypeWillChange] attribute should be used to temporarily suppress the notice (Fixed in Make CookieStore compatible with IteratorAggregate::getIterator #5010)
• During inheritance of php_user_filter: Uncaught ErrorException: Return type of CodeIgniter\Test\Filters\CITestStreamFilter::filter($in, $out, &$consumed, $closing) should either be compatible with php_user_filter::filter($in, $out, &$consumed, bool $closing): int, or the #[ReturnTypeWillChange] attribute should be used to temporarily suppress the notice (Fixed in Make CITestStreamFilter compatible with php_user_filter #5014)
• predis/predis related incompatible signatures (Fixed in Add ReturnTypeWillChange attribute to CursorBasedIterator predis/predis#708)
• During inheritance of DateTime: Uncaught ErrorException: Return type of CodeIgniter\I18n\Time::__wakeup() should either be compatible with DateTime::__wakeup(): void, or the #[ReturnTypeWillChange] attribute should be used to temporarily suppress the notice (Fixed in Make Time compatible with DateTime #5022)
• mikey179/vfsstream related incompatible signatures (Fixed in Add annotations to indicate return type will change bovigo/vfsStream#261)
• During inheritance of JsonSerializable: Uncaught ErrorException: Return type of CodeIgniter\Entity\Entity::jsonSerialize() should either be compatible with JsonSerializable::jsonSerialize(): mixed, or the #[ReturnTypeWillChange] attribute should be used to temporarily suppress the notice (Fixed in Add ReturnTypeWillChange attribute to Entity #5028)
• During inheritance of SplFileInfo: Uncaught ErrorException: Return type of CodeIgniter\Files\File::getSize() should either be compatible with SplFileInfo::getSize(): int|false (Fixed in Make File compatible with SplFileInfo #5040)
• Usage of static variables in inherited methods (Fixed in Remove static variables for PHP 8.1 #5262)
• Passing null to parameters historically allowing to pass null but now explicitly disallowing so. (Fixed in Fix deprecated usage of null on string params of internal functions #5371, Additional fix for deprecated null usage #5388)
• Precision loss on conversion of float to int. (Fixed in Fix precision loss deprecation on float to int conversion #5370)
• Compatibility with PgSql\Result (Fixed in Fix compatibility of Postgres result for PHP 8.1 #5278, Fix compatibility of PgSql\Result on closing the result instance #5279)

Checklist:

• Securely signed commits

[paulbalandan]

Initial incompat we have is the session handlers extending SessionHandlerInterface.

During inheritance of SessionHandlerInterface: Uncaught ErrorException: Declaration of
CodeIgniter\Session\Handlers\ArrayHandler::gc($maxlifetime): bool should be compatible
with SessionHandlerInterface::gc(int $max_lifetime): int|false

[lonnieezell]

Where are we at on this? It's a couple months old now, and I'd love to get some of these cleaned up and either merged or closed.

[MGatner]

Glad this is going smoothly! Should make for an easy transition this fall so we can focus on the 7.4 minimum.

[paulbalandan]

I'll be splitting unrelated changes in separate PRs.

[paulbalandan]

All green 🎉

I just would have to comment. Tests in PHP 8.1, excluding MySQLi, are pretty fast. Slow tests are now between 20-30 tests.

[MGatner]

That's awesome! I'm excited to see what dropping 7.3 does to our overall Actions runtime. If 8.1 is noticeably faster would should be looking at a sizable improvement.

8.1 should land today! Merge when you're ready.

[MGatner]

Just in time! 8.1 is now stable on setup-php: https://github.com/shivammathur/setup-php/releases/tag/2.16.0