tmp_path: This is the server's temporary file location path. this is used by the os to store temporary files.
app_root_dir: This is the physical directory location where the Sri application is installed on the server.
If the application is installed on your server in the html directory of your Apache server in a Centos installation then this path will be /var/www/html.
However If the application is installed as a virtual directory then it could be /var/www/sri . Where sri is the final directory containing the application.
Note: the application needs directory access to read, write and access permissions. Ensure that apache user has access.
base_dir : This is the base directory.
public_path: This is the directory which will contain public facing documents and images. The logo's and other web images are served from this directory.
Note: ensure that this directory is not public writable.