Description:
------------
When including a file, require_once() will make a destinction between path/file strings containing forward slashes and backslashes. 

Reproduce code:
---------------
(example)
function __autoload($className){
    $basePath = 'C:/htdocs';
    $classPath= $basePath . '/classes';
    require_once($classPath . "/$className.class.php");
}

// Some function that doesn't resolves paths
function getPath($file){
   $path = realpath('./$file');
   return $path;
}   

// Autoload
$A = new Foo;

// Explicit require of class
require_once(getPath(Foo.class.php));
$B = new Foo;

Expected result:
----------------
One would expect the require_once to notice that Foo has already been loaded and not include the file a second time.

Actual result:
--------------
Fatal error: Cannot redeclare class foo in c:\htdocs\classes\Foo.class.php on line n

(or something like that)

Whatever the actual result, the file is loaded twice, as the slashes produced by realpath are distinguished from the slashes used in the defined __autoload() function.