PHP - fix json_decode syntax error and set dev tools version

[mattiabasone]

What is the purpose of the change

Fix error reported by static analysis tool (phpstan)

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

[martin-g]

Thank you, @mattiabasone !

[RyanSkraba]

Thanks! Is this something that needs to be cherry-picked to branch-1.12?

[mattiabasone]

Thanks! Is this something that needs to be cherry-picked to branch-1.12?

Yes, please 🙂

[RyanSkraba]

Hello! I couldn't cherry-pick this because of merge conflicts -- do you want to give it a try or does it need to be rewritten for 1.12?

[mattiabasone]

Hello! I couldn't cherry-pick this because of merge conflicts -- do you want to give it a try or does it need to be rewritten for 1.12?

I've checked again the 1.12 branch, but it doesn't include the errors becuse the php source code is still outdated. @RyanSkraba is it probably related to the revert of this PR which added my recent changes