Kohana includes several tools to help you debug your application.
The most basic of these is Debug::vars. This simple method will display any number of variables, similar to var_export or print_r, but using HTML for extra formatting.
// Display a dump of the $foo and $bar variables
echo Debug::vars($foo, $bar);
Kohana also provides a method to show the source code of a particular file using Debug::source.
// Display this line of source code
echo Debug::source(__FILE__, __LINE__);
If you want to display information about your application files without exposing the installation directory, you can use Debug::path:
// Displays "APPPATH/cache" rather than the real path
echo Debug::path(APPPATH.'cache');
If you are having trouble getting something to work correctly, you could check your Kohana logs and your webserver logs, as well as using a debugging tool like Xdebug.