PDF Upload and Approval System

I'm looking for a simple PHP application that allows users to upload PDFs and manage their approval status.

Key Features:
- File Upload: Users can upload PDFs via `upload.php`. Files will be saved in the database as either base64 or BLOB.
- File List: `index.php` will show a list of uploaded files organized by approval status. Each entry should display the file name, upload date, and approval status.
- File Viewing & Approval: `view.php` will allow users to view and approve/decline files. Utilize the PDF.js Express library for editing and adding comments. After commenting and signing, the modified files should be saved to the database.
- Database: Use MySQL to store files, their approval status, and a hash key.
- No Authentication: The system should be accessible without any login or role-based access control.
- Code Quality: The code should be clean and well-structured for easy understanding.

Ideal Skills:
- Proficiency in PHP and MySQL
- Experience with PDF manipulation in web applications
- Familiarity with JavaScript and the specified PDF.js Express library
- Ability to write clean, maintainable code

Please ensure that your solution meets these requirements.