problem of require_once() with relative path.. is it a bug or normal behaviour

say if i do an include within an include an if i use relative paths it does not work.

HTML Code:
```i have directory structure as follows:
<pre>
c:\web -- index.php
c:\web\framework --- errorhandler(folde),debugger (folder), index.php

c:\web\framework\errorhandler -- class.error.php
</pre>```
1) c:\web\index.php -- include("framework/include.php") //correct

2) c:\web\include.php -- include("errorhandler/class.error.php //correct

3) c:\web\framework\errorhandler\class.error.php -- a) include("../include.php")//wrong error saying cannot open dtream
b) include("include.php")/right

3(b)should be wrong but in actual its viceversa.
3(a)is wrong and 3(b) is right

is it a bug or is it supposed to be like this.