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To: internals@lists.php.net,Dmitry Stogov <dmitry@zend.com>
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Date: Mon, 17 Dec 2007 13:17:32 -0500
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Subject: Re: [PHP-DEV] Re: Idea for namespace lookup resolution
From: jrhernandez05@gmail.com (Jessie Hernandez)

Dmitry,

As I mentioned, I did not find any significant performance penalty with 
this patch. Also, the patch can be improved by not checking the 
__get_namespace_classes function if we are not currently inside a namespace.

Either way, if we ignore namespace imports, then the best solution would 
be the following: commit Greg's patch which allows "use ::globalName", 
don't generate an error when a class is imported with the same name as 
an internal class, and modify the lookup logic so that internal classes 
are not even considered when inside a namespace. For example:

a.php
<?php
namespace ns;
$a = new Exception( 'test' ); // looks for ns::Exception
?>

b.php
<?php
$b = new Exception( 'test' ); // not inside namespace, so use 
::Exception directly
?>

The lookup rules would be:

1. Are we inside a namespace? No -> look for internal class named 
Exception. Yes -> look for ns::Exception.
2. If inside a namespace, and ns::Exception does not exist, then try 
autoloading ns::Exception.
3. If ns::Exception does not exist now, then generate an error.


The above would be consistent with how global variables are handled 
currently. In order to use a global variable inside a function, you 
first need to "import" it using a "global $name" statement. The same 
would apply here, in order to use a global/internal class, you either 
need to reference it using ::name syntax or have a "use ::name" 
statement at the beginning of the file. Since there aren't many internal 
classes in the first place, there will be few "use ::internalName" 
statements per file, so this won't burden the user.

I'll try to come up with the patch soon, incorporating Greg's "use 
::name" change.



Regards,

Jessie Hernandez
Zend Certified Engineer (http://zend.com/zce.php?c=ZEND006359&r=222727282)


Dmitry Stogov wrote:
> Hi Jessie,
> 
> The namespace may include several files and it may be extended with 
> additional files in any moment. So having single 
> __get_namespace_classes() function will require to update it every time 
> you extend namespace.
> 
> Also such function will significantly slowdown access to internal 
> classes. (It was the main reason why __autoload() was moved after check 
> for internal class).
> 
> Thanks. Dmitry.
> 
> Jessie Hernandez wrote:
>> Attached is the proof-of-concept patch. If the idea is met well, then 
>> I'll keep working on it to add caching and, if there's interest, I'll 
>> add *namespace imports*.
>>
>> An example of how a class in a namespace that's named the same as an 
>> internal class can be loaded:
>>
>> autoload.php
>> <?php
>> function __autoload($className)
>> {
>>     include_once str_replace( '::', DIRECTORY_SEPARATOR, $className ) 
>> . '.php';
>> }
>>
>> function __get_namespace_classes($namespaceName)
>> {
>>     return array( 'Exception' );
>> }
>> ?>
>>
>> test.php
>> <?php
>> namespace ns;
>>
>> include 'autoload.php';
>> $ex = new Exception();
>> var_dump( $ex ); // prints out ns:Exception instead of Exception
>> ?>
>>
>>
>> I ran a few tests on it and did not find any significant performance 
>> hit. If possible, I'd like someone to try it out and see if they have 
>> the same result.
>>
>> As always, comments/suggestions on the patch are welcome.
>>
>>
>> Regards,
>>
>> Jessie Hernandez
>> Zend Certified Engineer 
>> (http://zend.com/zce.php?c=ZEND006359&r=222727282)
>>
>>
>> Jessie Hernandez wrote:
>>> I just thought of something that might be a solution to the lookup 
>>> rules that we currently have in the namespaces implementation. 
>>> Whether it's good or not, I just wanted to throw it out there. Here 
>>> goes:
>>>
>>> Support a user-defined function named __get_namespace_classes, which 
>>> will be similar to __autoload. The signature of the function would be 
>>> the following:
>>>
>>>
>>> array __get_namespace_classes(string $namespaceName);
>>>
>>> Returns an array of names of classes that are under the specified 
>>> namespace, or FALSE if the classes under the namespace could not be 
>>> determined.
>>>
>>>
>>> The above function would be used in the lookup rules as follows 
>>> (using DateTime as an example):
>>>
>>> 1) Does the class DateTime exist in the current namespace?
>>> 2) If not, and the function __get_namespace_classes exists, call 
>>> __get_namespace_classes.
>>> 3) If the string DateTime is returned in the array from 
>>> __get_namespace_classes, then autoload that class.
>>> 4) If the class is not in the resulting array, or if the result was 
>>> FALSE, then look for an internal class DateTime.
>>>
>>>
>>> With the above function, you can define classes inside your namespace 
>>> that are named the same as internal classes without having to 
>>> explicitly "use" them all over the place. You also solve the problem 
>>> of namespace imports (sorry, use :-) ):
>>>
>>> <?php
>>> use PEAR::Net::*;
>>>
>>> $a = new FTP();
>>>
>>> // The above "use" statement results in calling the
>>> // __get_namespace_classes function and "using" each class in the
>>> // resulting array internally. Meaning the above will be equivalent to
>>> // this:
>>> //
>>> // use PEAR::Net::Curl;
>>> // use PEAR::Net::DNS;
>>> // use PEAR::Net::FTP;
>>> // ...etc...
>>> ?>
>>>
>>>
>>> For the above function to work best, the PHP "dir" function, as an 
>>> example, should be modified to have an additional "use_include_path" 
>>> argument:
>>>
>>> object dir(string $directory [, bool $use_include_path])
>>>
>>>
>>> By passing TRUE as the second argument, the directory will be 
>>> searched for in the include path. The user can then do something like 
>>> the following as an implementation of __get_namespace_classes 
>>> (assuming the user organized it into class per file, as is common):
>>>
>>> <?php
>>> function __get_namespace_classes($namespaceName)
>>> {
>>>     $classes = false;
>>>     $nsDir = str_replace( '::', DIRECTORY_SEPARATOR, $namespaceName );
>>>     $d = dir( $nsDir, true );
>>>
>>>     if( $d )
>>>     {
>>>         $classes = array();
>>>
>>>         while( ( $file = $d->read() ) !== false )
>>>             $classes[] = str_replace( '.php', '', $file );
>>>
>>>         $d->close();
>>>     }
>>>
>>>     return $classes;
>>> }
>>> ?>
>>>
>>>
>>> Let me know what you think!
>>>
>>>
>>>
>>> Regards,
>>>
>>> Jessie
>>