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Date: Mon, 16 Apr 2012 07:55:17 -0500
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To: Simon Schick <simonsimcity@googlemail.com>
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Subject: Re: [PHP-DEV] New Feature: Fully qualified class name resolution
 as scalar with class keyword
From: ralph@ralphschindler.com (Ralph Schindler)

Hey Simon,

> As the class-definition for Moo is missing, I think it's an empty
> class (like Baz) on the root-level defined somewhere else, right?
> Otherwise this should do something else than guessing the class-name.

If you look at the patch, this feature is not doing anything PHP doesn't 
already do in other circumstances - demonstrated by the fact that its 
only about 4 lines of code ;)

In PHP, in situations like (instanceof):

   if ($foo instanceof Bar)

or (catch)

   } catch (SomeException $e) {

or (method signature)

   public function setFoo(FooInterface $foo)

... PHP does not invoke the autoloader to determine if the class name 
actually exists as a declaration somewhere, it simply resolves it 
according to some very specific rules (in the case of this patch, 
carried out by zend_resolve_class_name()).

If I am within a namespace and am using a short name without a preceding 
"\", it means the class I am referencing exists in the current 
namespace.  Whether or not that class exists is irrelevant as my short 
name can only mean "a class by this name in the current namespace".  In 
this code:

   namespace Foo\Bar {
     global $foo;
     if ($foo && $foo instance Bar) {
         // ...
     }
   }

... that you, the developer, intend that your reference to Baz actually 
means "Foo\Bar\Baz", it can never mean anything else.

So, in a nutshell, there is no guessing going on ;)
-ralph