Idea for namespace lookup resolution View as Markdown

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