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Date: Fri, 15 Feb 2013 20:04:24 -0700
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To: Sanford Whiteman <swhitemanlistens-software@cypressintegrated.com>
Cc: Nikita Popov <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Questions regarding DateTimeImmutable
From: morrison.levi@gmail.com (Levi Morrison)

> I think it was done to ease adoption even though it was known to
> violate LSP. To quote Stas, "As for established practice, everybody
> expects DateTime, so IMHO we should leave DateTime as base class even
> though it's not strictly OO-pure."

I can see how easing adoption would be logical, but honestly I don't
think this will help.  Just because the outward API *looks* the same,
a DateTimeImmutable is NOT a drop in replacement for DateTime. I
honestly think that having one or the other inheriting from the other
isn't *just* an LSP violation: it's a really big one. It's so big I
don't think there's much worth of having them inherit; I dare say it
would hurt it.

> This way does let users sub in DateTimeImmutable more easily and patch
> over a ton of unintended -- maybe not even fully noted or understood
> -- defects in their apps? I dunno.

Exactly.