What potential pitfalls should be considered when using nested include statements in PHP?

When using nested include statements in PHP, one potential pitfall to consider is the possibility of including the same file multiple times, leading to redeclaration errors or unexpected behavior. To avoid this issue, you can use the `require_once` or `include_once` functions instead of `require` or `include` to ensure that a file is only included once.

// Example of using require_once to include a file without the risk of redeclaration
require_once 'config.php';