php get namespace of included file

Question

//file foo.php
<?php
namespace foo;
class foo{
    function __construct(){
        echo "hello";
    }
}
?>

//file index.php
<?php
require_once("foo.php");
echo __NAMESPACE__;
?>

My question is, from my index.php file, is it possible to know what the namespace of foo.php is without reading the file contents and doing a regular expression on it? That just seems like a lot of overhead.

///EDIT

I'd really like to be able to dynamically add the namespace to the included file.

<?php
namespace dynamic;
require_once("foo.php");
echo __NAMESPACE__;
?>

I want to allow for third-party plugins, but php namespaces seems terrible. I don't want to have the plugin editors have to create a namespace.

Answer 1

No. But you could trick it this way round:

//file foo.php
<?php
  namespace foo;
  //...
  return __NAMESPACE__;  // must be last line
?>

And for reading it out:

//file index.php
<?php
  $ns = require_once("foo.php");

Answer 2

Well, you could scan the class namespace. It contains namespaces. It's the PHPUnit way of doing things. So i.e.:

$namespaces = get_current_namespaces();

include 'plugin/main.php';

$newNamespaces = get_current_namespaces(); 
array_diff($namespaces, $newNamespaces)

Here is how you can implement get_current_namespaces(): is it possible to get list of defined namespaces

Answer 3

If you know the file, you can simply extract the namespace form it :).

function extract_namespace($file) {
    $ns = NULL;
    $handle = fopen($file, "r");
    if ($handle) {
        while (($line = fgets($handle)) !== false) {
            if (strpos($line, 'namespace') === 0) {
                $parts = explode(' ', $line);
                $ns = rtrim(trim($parts[1]), ';');
                break;
            }
        }
        fclose($handle);
    }
    return $ns;
}

And you will be not constrain to return something at the end of file that can be broke from exit or other return instructions.