Usage of fopen/fwrite/fclose in WordPress theme

Hi everybody,

I’m trying to create a file by using the following code in my sidebar.php:

$file = fopen("file.xml", "w");
fwrite($file, $xml);
fclose($file);

I tested the script outside WordPress and it works fine, however, when using it within WP I get an error message saying

Warning: fopen(file.xml) [function.fopen]: failed to open stream: Permission denied in sidebar.php on line 46

Warning: fwrite(): supplied argument is not a valid stream resource in sidebar.php on line 47

Warning: fclose(): supplied argument is not a valid stream resource in sidebar.php on line 48

Any idea what’s wrong? the file exists already and has CHMOD 777 and as I stated before the script works fine when used stand alone.

Cheers
Felix