Support for DateTimeInterface

[rquadling]

Hi.

Wanting to use DateTimeImmutable for DateRange, but the typehint is current DateTime.

Moving to DateTimeInterface would be ideal, but this is PHP5.5+ only.

Polyfilling of the DateTimeInterface and DateTimeImmutable is all possible, but the issue is that you cannot add the DateTimeInterface to DateTime so you would lose compatibility at some stage.

Maybe a branch for PHP5.5+ that uses DateTimeInterface typehint, rather than DateTime would be nice.

[gws]

Yeah, I agree with this.

I'm OK cutting a new release which just uses DateTimeInterface and drops support for anything less than PHP 5.5. PHP 5.4 is EOLed and people can continue to use older releases of this project if they cannot upgrade.

I'd also rather use DateTimeImmutable internally which would make all of the defensive cloning unnecessary.

[rquadling]

Sounds good.

[rquadling]

Hi. Time to do this now then? I think a major release that requires PHP7+? PHP 5.5 is now security fixes only.

[gws]

@rquadling I opened #9 for this.