I have the following files:

```
/Index.php
/someFolder/somefile.php
/someFolder/DataBase.php
/config/config.xml

```

In `Index.php` I have included `DataBase.php`:

```
include_once('someFolder/DataBase.php');

```

In `somefile.php` I have included `DataBase.php`:

```
include_once('DataBase.php');

```

Now I want to open `config.xml` from `DataBase.php`:

```
simplexml_load_file('config/config.xml');

```

If I access `config.xml` from `DataBase.php`, which I included in `Index.php` it works, but If I do it from `DataBase.php`, which I included in `somefile.php` I have an error:

```
I/O warning : failed to load external entity

```

How to deal with it ?