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Date: Tue, 25 Feb 2025 22:51:40 +0000
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Subject: Re: [PHP-DEV] Consensus gathering: allowing unsetting of backed
 property hooks
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From: imsop.php@rwec.co.uk ("Rowan Tommins [IMSoP]")

On 25/02/2025 21:13, tight.fork3192@fastmail.com wrote:
> Hello! I started GitHub issue requesting that property hooks be allowed to be `unset()`:https://github.com/php/php-src/issues/17922
>
> While discussing in the issue it was suggested I pitch this to the mailing list, so here I am.


Place me firmly in the "unset() is already weird enough" camp.

I actually started writing an RFC to rationalise some of this behaviour, 
but gave up because it's such a mess.

Here are some of the things that might happen as a result of 
unset($foo->bar):

* Nothing at all, because unsetting a non-existent property isn't even a 
Warning
* A dynamic property (not declared, but created because it was assigned 
a value) is deleted without trace
* A property declared with no type becomes "undefined", and appears to 
be deleted (e.g. disappears from var_dump) ...
* ... but retains its visibility (e.g. you'll still get an error writing 
to it from outside the class if it's private)
* A property declared *with* a type (even if that type is "mixed") 
instead becomes "uninitialized" - it still appears in var_dump, and 
accessing it is an Error, instead of a Warning
* An __unset() handler might be called ...
* ... even if the property is declared, but is currently "undefined" or 
"uninitialized" ...
* ... and that handler could do absolutely anything, including throwing 
an exception

If we allow a hooked property to directly "unset" the backing value, 
what *exactly* will it do? And what if it's a virtual property, so there 
is nothing to unset? If we add an "unset" hook, what's the default 
behaviour if one isn't defined?

I think it's one of those features that sounds simple when you look at a 
single use case, but actually specify the behaviour in all cases is 
going to be a lot of work.

-- 
Rowan Tommins
[IMSoP]