What steps can be taken to troubleshoot and resolve issues with file inclusion errors in PHP applications like osCommerce?

File inclusion errors in PHP applications like osCommerce can be troubleshooted and resolved by checking the file paths and permissions, ensuring that the files being included actually exist in the specified location, and using the correct syntax for including files. Additionally, using absolute paths instead of relative paths can help avoid issues with file inclusion errors.

// Example of using absolute paths to include files in osCommerce
include_once(__DIR__ . '/path/to/file.php');