\Ibexa\Contracts\Rest\Output\Generator::startValueElement contract doesn't declare 3rd argument array $attributes while both existing implementations:

• \Ibexa\Rest\Output\Generator\Json::startValueElement
• \Ibexa\Rest\Output\Generator\Xml::startValueElement

declare and use it. Moreover in case of Json there's no way to work around it with the current API.

Technically it's a BC break for someone extending Generator, however within PHP Team we've assessed this to be unlikely scenario. The change to those generators was introduced 11 years ago and was never propagated to the abstract, so at this point this is just a bug causing static analysis issue.

Due to BC-breaking nature of the fix, it's aimed to be fixed in 4.6.0 and higher only.