What potential issue can arise when using "require" in PHP to include files via the HTTP protocol?

When using "require" in PHP to include files via the HTTP protocol, a potential issue that can arise is that it can make your application vulnerable to remote file inclusion attacks. To solve this issue, you should avoid including files from remote servers and instead include files using local file paths.

// Example of including a file using a local file path
require_once(__DIR__ . '/path/to/file.php');