Objective: Create a simple and secure login system with php + mysql script

1. Develop a user registration with input validation
   1. Check for duplication of user names
   2. Check password complexity
   3. Allow password confirmation
2. Your code must include input validation for normal logins:
   1. Password complexity (1 upper, 1 lower, 1 numeric and 1 special character)
   2. Password length
   3. Password history
3. Develop a secure password recovery.