在包含文件中没有在类函数中声明的全局？ [关闭]

Take the following php class:

 class test
 {
    function do_it_to_it(){
        global $path;

        if(somecondition){
           $path = 'path/to/goodies';
           require_once('some_file');
        }
    }
 }

The contents of "some_file" are as follows:

global $path;
define('GOODIEPATH', $path); 

Now I call:

$t1 = new test();
$t1->do_it_to_it();

$path in "some_file" will be null instead of "path/to/goodies." I have a feeling that this is because $path is either being overwritten for some reason by the second "global $path" or because of some type of global scope issue. What am I missing here?

P.S. - I hate globals more than anybody, but I can't fix it in this case without breaking legacy code.

EDIT: I have revised the test class above to show an if statement that is present in the real code. I seem to have resolved the issue by moving the global statement inside the if statement, like so:

class test
{
   function do_it_to_it(){

     if(somecondition){
        global $path;
        $path = 'path/to/goodies';
        require_once('some_file');
     }
   }
}

Any idea why this seems to fix it? The if statement causes the original global declaration to be out of scope somehow?

I always recommend to define global variables on the zero level of the code for example in separate file and include this file in all sources.