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To: "Sherif Ramadan" <theanomaly.is@gmail.com>
Cc: "Nikita Popov" <nikita.ppv@gmail.com>, "Clint Priest"
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Date: Sun, 20 Jan 2013 15:21:03 +0100
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Subject: Re: [PHP-DEV] [VOTE] Property Accessors for 5.5
From: glopes@nebm.ist.utl.pt ("Gustavo Lopes")

On Sun, 20 Jan 2013 14:52:36 +0100, Sherif Ramadan  
<theanomaly.is@gmail.com> wrote:

>> I think the current behavior is most appropriate one for var_dump() (and
>> array casts/get_object_vars()). It's the same behavior as if you had
>> manually defined getXXX() methods or used __get().
>>
> It's actually not the same behavior at all. __get can only work on
> inaccessible properties. So I would not see NULL there in the object and
> then get a value in the instance property.

OK, it's not 100% analogous. And I'm ready to concede that the differences  
that do exist may be (arguably) sufficient to draw a principled  
distinction, namely:

* getXXX() is clearly a method call and not a (direct) property read and  
the XXX property may not even exist.
* __get() only works on inaccessible properties, so there is no possible  
confusion.

I still think you put too much emphasis on the __get() argument -- even  
though there is no accessible property, there may be a protected/private  
property; it it isn't the case, there's still usually some backing  
storage, like a private array (shown in var_dump()) and the backing value  
may be different from what's returned.

In any case, assuming this feature is accepted, the current solution,  
whether in isolation it's appropriate or not, must be evaluated in the  
light of the alternatives. Here, I thought you were proposing calling the  
getters.

>> If you start marking function calls, you get new problems like handling
>> getters that throw exceptions or have side effects ("the code behaves
>> differently when add a var_dump()?!").
>
>
> I'm not suggesting the getters should be invoked from afar. I'm just
> suggesting some additional means of informing the user of the existence  
> of that getter to distinguish it from the property in the output of  
> var_dump.
>
> So for example, in var_dump, you can get ["property":protected] => ...  
> when the property has a visibility outside of the current context. It  
> might be
> helpful to provide some similar behavior for accessors with null
> initialized values, but have getters available to the caller?

We could add some sort of marker to indicate the property is an accessor.  
It would not be trivial under the current implementation as  
get_properties() and get_debug_info() only return a HashTable*, so some  
abstraction breaking would be required.

Another possibility would be the ability to mark some properties as not  
backed by any storage, like the area in your example. But this would still  
be insufficient to eliminate confusion in cases like this:

class A {
	private $scale;
	public $value {
		get { return $this->value * $this->scale; }
		set;
	}
	function __construct($scale) { $this->scale = (double)$scale; }
}

-- 
Gustavo Lopes