Add PHPDoc return types

[ruudk]

Symfony PHPUnit Bridge has a deprecation helper that warns when things might break in the future.

It currently reports the following errors when using Stripe PHP SDK:

Method "ArrayAccess::offsetExists()" might add "bool" as a native return type declaration in the future. Do the same in implementation "Stripe\StripeObject" now to avoid errors or add an explicit @return annotation to suppress this message.
Method "ArrayAccess::offsetGet()" might add "mixed" as a native return type declaration in the future. Do the same in implementation "Stripe\StripeObject" now to avoid errors or add an explicit @return annotation to suppress this message.
Method "ArrayAccess::offsetSet()" might add "void" as a native return type declaration in the future. Do the same in implementation "Stripe\StripeObject" now to avoid errors or add an explicit @return annotation to suppress this message.
Method "ArrayAccess::offsetUnset()" might add "void" as a native return type declaration in the future. Do the same in implementation "Stripe\StripeObject" now to avoid errors or add an explicit @return annotation to suppress this message.
Method "Countable::count()" might add "int" as a native return type declaration in the future. Do the same in implementation "Stripe\StripeObject" now to avoid errors or add an explicit @return annotation to suppress this message.
Method "JsonSerializable::jsonSerialize()" might add "mixed" as a native return type declaration in the future. Do the same in implementation "Stripe\StripeObject" now to avoid errors or add an explicit @return annotation to suppress this message.

By adding these PHPDoc types, the problem disappears. It's also more clear for users of the package.

Fixes #1210

[CLAassistant]

All committers have signed the CLA.

[axi]

So I'll just wait for it to be merged, thanks

[ruudk]

@yejia-stripe What do you think of this? Can it be merged?

[dcr-stripe]

@richardm-stripe will review as they were looking at #1210.

[ruudk]

Any news?

[jokaorgua]

@dcr-stripe do you have any news?

[henrikac]

Any updates on this?

[remi-stripe]

Hey everyone, sorry for the radio silence on that one. I'll raise this internally and get you a clearer answer/update next week.

[richardm-stripe]

Sorry for the silence, presently this PR cannot be merged as type errors are causing it to fail CI. I will spend some time to see if it can be repaired.

[richardm-stripe]

Seems to have been an unrelated problem in the particular SHA of the master branch -- merging the latest has fixed the problem. Everything seems to be in order -- thanks for the contribution!

[ruudk]

Thanks, would be great to have this tagged too 🙏