How can file paths be correctly referenced in PHP to avoid errors like "File or Directory not found" or "Permission denied"?

To avoid errors like "File or Directory not found" or "Permission denied" in PHP when referencing file paths, it is important to use the correct path format and ensure that the necessary permissions are set for the files or directories being accessed. Using absolute paths or relative paths correctly can help avoid these errors.

// Example of using absolute path to include a file
include_once('/path/to/file.php');

// Example of using relative path to include a file
include_once('../folder/file.php');