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Date: Sat, 14 Feb 2015 00:25:12 +0100
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To: PHP internals <internals@lists.php.net>
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Subject: Re: [RFC] Exceptions in the engine
From: nikita.ppv@gmail.com (Nikita Popov)

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On Mon, Oct 6, 2014 at 11:53 PM, Nikita Popov <nikita.ppv@gmail.com> wrote:

> Hi internals!
>
> During the PHP 5.6 development cycle I have proposed an RFC [1] that
> suggested the use of exceptions instead of fatal errors in the engine. At
> the time the proposal was declined, because the change was judged too
> intrusive for a minor version.
>
> As such I'm re-proposing this RFC for inclusion in PHP 7:
>
>     https://wiki.php.net/rfc/engine_exceptions_for_php7
>
> The RFC text is essentially the same as previously, with the primary
> difference being that parse errors are now converted to exceptions as well.
> This was previously not possible due to limitations in the compiler design.
>
> Thanks,
> Nikita
>
>   [1]: https://wiki.php.net/rfc/engine_exceptions
>

Feature freeze is not so far away now, so I'd like to bring this RFC up
again and proceed to voting shortly. There are two primary open questions:

 * Subclassing: Should there be more specific subclasses of EngineException
for particular errors?
 * Superclassing: Should EngineException inherit from Exception (and as
such be subject to catch(Exception)) or should we introduce some kind of
special super-class that is not caught by default (like
Catchable/Throwable)?

I don't think we can implement a high-quality subclassing scheme in a
timeframe for PHP 7, as such I would suggest to postpone this (if we
actually want to do it) to a later point in time. We can introduce
subclasses without BC issues in a minor version.

The question of whether EngineException should inherit from Exception is
something we do have to consider now. Personally I prefer not introducing
any special exception types that aren't caught by default. I think that
would only make sense for errors that could occur literally everywhere
(like memory limit or timeout), but these are not handled by this RFC for
technical reasons. If someone has a strong opinion on this, I might make it
a voting option.

Commentary on these, and also any other relevant points is very welcome!

Thanks,
Nikita

PS: The patch attached to the RFC is very outdated. I plan to only update
it to current master once the RFC passes (if it does), as I already had to
practically rewrite it a few times.

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