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To: Christian Schneider <cschneid@cschneid.com>
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Subject: Re: [PHP-DEV] namespace separator and whining
From: greg@chiaraquartet.net (Gregory Beaver)

Christian Schneider wrote:
> Lukas Kahwe Smith wrote:
>> one could also do
>> 1) ns
>> 2) global
>> 3) autoload
> 
> I'm in favour of this (if it avoids performance problems) as I don't see
> a problem with giving global priority over autoload.

Hi,

This is the current name resolution.  The problem is that:

<?php
namespace foo;
$a = new Exception();
?>

will instantiate foo::Exception only if the class already exists, but
will instantiate Exception otherwise.  This defeats autoload's purpose
for existing.  We've been over this before.  It's dangerous.

There is one essential difference between classes and
functions/constants: autoload.

The only time the question of load order and fallback becomes and issue
is when code is not explicitly loaded.  In other words, a developer who
is relying upon an external function will do this at some point before
calling the function:

<?php
include 'path/to/code/containing/function/source.php';
?>

In other words, PHP expects you to actually load the source of functions
or constants you're going to be using in advance of using it.

This, I believe, is a reasonable expectation.

Classes, however, do *not* share this same expectation, because
autoload's explicit purpose is to allow using classes *before* their
source has been loaded.

In other words, it is perfectly all right to have a different name
resolution for classes than we have for functions and constants because
of this different expectation.  It is dangerous to fallback for classes
prior to autoload, but it is not at all dangerous for
functions/constants because the expectation is different.

For this reason, the only resolution that we should be considering is:

classes:
1) try ns::class
2) autoload ns::class
3) fail

functions/constants:
1) try ns::function/ns::const
2) try internal function/const
3) fail.

Note that I say "try internal" because the only purpose behind allowing
this is to make it easier to use PHP's built-in functionality.  Any
userspace stuff should be specifically \prefixed or imported via use.
And (yes) we need import for functions.

Greg

P.S. my mail server has been down for almost a week, apologies to anyone
who is wondering why I haven't replied to your message, I probably
didn't get it.