GetRootPath in PHP connector

Symlinks can cause this to fail... surely we should just use "return $_SERVER['DOCUMENT_ROOT']" or use this variable in the actual scripts?

Refs:
Function GetRootPath() in /editor/filemanager/browser/default/connectors/php/io.php
Function GetRootPath() in /editor/filemanager/upload/default/connectors/php/util.php