- [X] [[ https://wiki.php.net/rfc/throwable-interface | Add `Throwable` interface ]]
(WARNING) `Error` should not extend `Exception` but `Throwable`
- [X] [[ https://wiki.php.net/rfc/preg_replace_callback_array | Add `preg_replace_callback_array()` internal function ]]
- [ ] [[ https://wiki.php.net/rfc/anonymous_classes | Anonymous Classes ]]
- [ ] [[ https://wiki.php.net/rfc/generator-delegation | Generators delegation ]]
NOTE: Firstly implement generators [ T6816 ]
- [X] [[ https://wiki.php.net/rfc/combined-comparison-operator | "Spaceship" operator ]] [ D6645 ]
- [X] [[ https://wiki.php.net/rfc/return_types | Return type declarations ]] [ D6643, D6675, D6680 ]
- [X] [[ https://wiki.php.net/rfc/isset_ternary | Null Coalesce Operator ]] [ D6645 ]
- [X] [[ https://wiki.php.net/rfc/closure_apply | `Closure::call()` internal function ]]
NOTE: Firstly implement closures object extension [ T6817 ]
- [ ] [[ https://wiki.php.net/rfc/group_use_declarations | Grouped namespaces ]]