What are the common errors that may occur when including PHP files and classes, and how can they be resolved?

Common errors when including PHP files and classes include using incorrect file paths, not properly including the necessary files, and namespace conflicts. To resolve these issues, ensure that the file paths are correct, use the correct include/require statement, and namespace your classes properly.

// Example of including a PHP file with correct file path and include statement
require_once 'path/to/file.php';