How can the use of short open tags in PHP code impact the inclusion of external files?

Using short open tags in PHP code can impact the inclusion of external files because short open tags might not be enabled on all servers, leading to syntax errors when trying to include files. To solve this issue, it's recommended to use the full `<?php` tag instead of short open tags.

// Instead of using short open tags like <?, use the full <?php tag
include 'external_file.php';