What is the significance of defining a constant like 'SMARTY_DIR' in PHP scripts, and what are the best practices for setting paths in such cases?

Defining a constant like 'SMARTY_DIR' in PHP scripts is significant for setting a base path that can be easily referenced throughout the code. This helps in maintaining consistency and makes it easier to update the path in a single location if needed. Best practice for setting paths in such cases is to define the constant at the beginning of the script or in a separate configuration file.

define('SMARTY_DIR', '/path/to/smarty/libs/');