strange php url

Hi, could anyone tell me why the following url doesn't generate a "page not found" ? http://www.php.net/manual/en/function.checkdnsrr.php/manual/ you can try with a longer url after the last .php. I tried with ../manual instead of manual and this produces a 404. I checked with www.php.net because my own site does the same and I wanted to be sure it didn't come from my config. thanks Nicolas Figaro