What are the best practices for defining paths when including PHP files in a project?

When including PHP files in a project, it's important to define paths in a way that is consistent and reliable across different environments. One common best practice is to use the `__DIR__` magic constant to reference the current directory of the file being executed. This ensures that paths are always relative to the current file, regardless of where the script is being run from.

// Define path to included file using __DIR__
include __DIR__ . '/path/to/file.php';