dynamic folder path

hey,

i just want to use the php function scandir() in my plugin files.

this works:

$folder = '/var/www/web157/html/com/wordpress-neu/wp-content/themes/test';
$allfiles = scandir($ordner);

this not:

$folder = '/wp-content/themes/test';
$allfiles = scandir($ordner);

Warning: scandir() [function.scandir]: (errno 2): No such file or directory

the problem: if someone wants to use my plugin the path has to be changed manually..

any ideas how to solve this?

thanks a lot
Jan