I’m bringing several in-house web modules under one roof and need a streamlined integration that centres on secure user authentication. The stack is already defined—HTML5, CSS3, vanilla JavaScript on the front end, with PHP 7+ and MySQL powering the back end—so your focus will be stitching everything together cleanly. What I need • A unified database schema for accounts, roles, and permissions. • Reusable PHP classes or a lightweight API that handles sign-up, login, password reset, and session validation. • Seamless hand-off of the authenticated session across my existing pages, preserving the current UI. • Functional tests that confirm login persistence, session timeout, and protection against common attacks (SQL injection, XSS). • Brief but clear documentation plus a quick hand-over video so I can extend the system easily. You’ll have SSH and phpMyAdmin access to a staging server, along with sample data to get started. Clean, well-commented code and adherence to best practices are essential. If you’ve delivered single-sign-on or similar integrations before, please share a quick link or description; that will help me move faster on awarding the project.