PHP/Mapscript + map object -> save method

[Wally Maddoc]

Hello All,

I'm trying to save a mapObject $map via its method $map->save(STRING
file_name). I always receive this error message:

Fatal error: [MapServer Error]: msSaveMap():
(/var/www/apache2-default/erik/map_files/test) in
/var/www/apache2-default/erik/examples/phpmapscript3.php on line 76

The code looks like this:

$map= ms_newMapObj(map_file_name);
...
$map->save("/var/www/apache2-default/erik/map_files/test");


Is there any bug in the mapObjectclass? 
Can anyone help me?

Thanks

Erik