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Date: Thu, 17 Jan 2013 19:42:37 -0600
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To: Steve Clay <steve@mrclay.org>
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Subject: Re: [PHP-DEV] [VOTE] Property Accessors for 5.5
From: cpriest@zerocue.com (Clint Priest)


On 1/17/2013 4:24 PM, Steve Clay wrote:
> > https://wiki.php.net/rfc/propertygetsetsyntax-v1.2#voting
>
> I'll say my peace on this. This is a very good implementation, and as 
> long as authors use accessors that depend on a separate property for 
> storage (like other langs require), everything will be 
> straightforward. Otherwise, I fear they're in for some confusing 
> behavior.
>
> Consider the code from the RFC:
>
> class TimePeriod {
>     public $Hours {
>         get { return $this->Hours ?: "not specified"; }
>         set { $this->Hours = $value; }
>     }
> }
>
> $tp = new TimePeriod();
> $tp->Hours; // "not specified"
> isset($tp->Hours); // true!?
>
$tp->Hours isset, the property exists and it's value is non-null.

> The auto implementation of isset compares $this->Hours to NULL, but 
> since $this->Hours goes through the getter, it will return "not 
> specified". So the property will always appear to be isset.
>
> * The guards seem spooky: A set of tokens ($this->prop) will have 
> varying behavior (e.g. direct prop read vs. getter call) *depending on 
> the call stack*.
This is the same as would occur with isset against an undefined 
property, that would call __isset(), followed by __get() which would 
then compare the value to NULL.
>
> * Giving issetter/unsetter no direct access to the property limits 
> functionality and leads to weirdness like the example above.
>
This is possible, simply by supplying your own implementation of 
isset/unset that calls isset/unset, such as:

public $foo {
     get; set;
     isset { return isset($this->foo); }
     unset { unset($this->foo); }
}

The above five lines of code is exactly equivalent in functionality to:

public $foo;

-Clint