Secure PHP MySQL Data Manager

I have a set of documents whose fields need to live in a MySQL database. Your task is to create a well-structured PHP script that does two things:

1. Forms for receiving data, on submission sanitize every field, and insert the data into MySQL using prepared statements so nothing slips past standard security checks.

2. Provide a responsive search form that exposes every stored field as an input variable. When a user submits the form, the script must build a safe, dynamic query, pull matching records, and render them clearly in a results table.

Core requirements
• PHP 8+ and MySQL 5.7/8.0
• Server-side validation, input sanitisation, and CSRF protection
• Config file for DB credentials kept outside web-root
• Neatly organised functions/classes so future maintenance is painless

Deliverables
– Clean, well-commented PHP source code
– MySQL schema (CREATE TABLE statements)
– Basic bootstrap-styled HTML for the form and results page
– README with setup steps and a brief security outline

I will provide a sample document set once we start; you return a zip or repo link ready to run.