Fix PHP 8.2 compatibility across core classes

[alex001x]

This PR improves compatibility with PHP 8.2 by cleaning up core class implementations.

Changes are intentionally minimal and focused on:

• Fixing deprecated or unsafe patterns in PHP 8.2
• Preventing warnings/notices (foreach on non-iterables, null handling, etc.)
• Improving robustness of PDO result handling
• Fixing minor logical issues discovered during the PHP 8.2 review

No functional changes or schema modifications are intended.
No refactoring or behavior changes outside PHP 8.x compatibility.

Each class was reviewed and committed independently to keep the diff readable and easy to audit.