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Date: Mon, 19 Jan 2015 12:30:09 +0100
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To: Stanislav Malyshev <smalyshev@gmail.com>
Cc: Dan Ackroyd <danack@basereality.com>, 
	"internals@lists.php.net" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Class constructor behaviour
From: tyra3l@gmail.com (Ferenc Kovacs)

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On Mon, Jan 19, 2015 at 6:41 AM, Stanislav Malyshev <smalyshev@gmail.com>
wrote:

> Hi!
>
> > This is pretty horrible and should be fixed by making sure that
>
> I don't see why it's so horrible. In fact, handling null is easier than
> handling exception (and faster too, probably). Many functions that try
> to create objects return null or false when unable to. Of course, we
> could change it by introducing exceptions to core, but I don't see why
> do it peacemeal then.
>
> > constructors either return an object or throw an exception.
> > Additionally the exception policy for core (that was previously
> > discussed here: http://marc.info/?t=3D119263748000001&r=3D1&w=3D2 ) sho=
uld
> > be updated so that any constructor returning NULL is considered a bug,
> > no matter what the ini settings are. To be clear, procedural code
> > should behave as before, with users expected to check for errors.
> > This would be a BC break for people who are handling the constructor
> > returning null currently, as they would need to wrap that code with an
> > try/catch block.
>
> That means the same failure of collator construction now needs to be
> handled in two different ways.
>
> > Constructors give warning, but are then in an unusable state
> > ------------------------------------------------------------
> > Several constructors check the parameters that they are given.....and
> > then just give a warning when they are not acceptable. e.g.
>
> These should be fixed to either return null or throw exception, but the
> behavior should be unified for everybody.
>
> > Again, this should be fixed by changing the constructors to throw an
> > exception if the input parameters are not acceptable.
>
> The next question would be - if the ctors throw an exceptions, why
> factory methods shouldn't? They are doing the same work essentially.
>
> > Constructor gives error
> > -----------------------
> >
> > Some constructors check the parameters they are given, and then emit
> > either a 'Catchable fatal error' error or other error e.g.
>
> This is even bigger can of worms. If we wrote PHP today from scratch,
> catchable fatal errors would be exceptions. But they are not, so we need
> to deal with it - by either leaving them as is, or converting them all
> together.
>
> >
> > <?php
> > $foo =3D new IntlGregorianCalendar(new StdClass);
> > //Output: Catchable fatal error: Object of class stdClass could not be
> > converted to string in..
>
> This is not property of the ctor, it's property of parameter handling.
> I.e. if you do it for IntlGregorianCalendar, you should do it for every
> class that gets incompatible parameters. And probably user-space funcs
> too since there's no reason for them to behave differently. I actually
> wouldn't mind that, but this is yet bigger can of worms as it requires
> refactoring a lot of assumptions on how parameters are parsed.
>
> > i) Can anyone see a big hurdle in fixing these behaviours, other than
> > it being a BC break for people who are currently relying on these
> > behaviours ?
>
> Yes. The first hurdle is to understand which of these behaviors need
> fixing, and how, which you seem to dismiss as obvious but it's really
> not. The second is to do it in consistent manner so it doesn't again
> come out as part of the functions do one thing, another part another,
> and third part something else different.
>
> > ii) Are there any other bad behaviours that people are aware of that
> > ought to be fixed at a major version?
>
> I think we have enough for now to discuss here, so if we want do discuss
> other behaviors better to open separate thread.
>
> --
> Stas Malyshev
> smalyshev@gmail.com
>
> --
> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: http://www.php.net/unsub.php
>
>
Hi,

AFAIK (based on
http://www.mail-archive.com/internals@lists.php.net/msg43237.html and other
discussions) errors in constructors should throw exceptions (even for
classes in core).

--=20
Ferenc Kov=C3=A1cs
@Tyr43l - http://tyrael.hu

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