# Security Fix Summary: Role-Based Access Control Enhancement

## Issue Description
The system had inconsistent role-based access control where teachers could potentially access admin pages, which violates the principle that teachers should only access their designated pages and not admin pages.

## Solution Implemented

### 1. Created Access Control Module
Created a new access control module at `includes/access_control.php` with the following functions:
- `require_admin()` - Ensures only admin users can access
- `require_teacher()` - Ensures only teacher users can access
- `require_student()` - Ensures only student users can access
- Helper functions for checking roles and permissions

### 2. Updated Admin Pages
Updated all admin pages to use strict access control:
- `admin/index.php` - Now uses `require_admin()` function
- `admin/users.php` - Now uses `require_admin()` function
- `admin/settings.php` - Now uses `require_admin()` function

### 3. Updated Teacher Pages
Updated teacher pages to ensure only teachers can access:
- `teachers/dashboard.php` - Now uses `require_teacher()` function and additional check to prevent admin access
- `teachers/routine.php` - Now uses `require_teacher()` function and additional check to prevent admin access

### 4. Key Security Enhancements
1. **Strict Role Checking**: Changed from loose comparison (`!=`) to strict comparison (`!==`) where appropriate
2. **Consistent Access Control**: All admin pages now consistently check for admin role only
3. **Teacher Isolation**: Teachers can no longer access admin pages even if they somehow bypass initial checks
4. **Centralized Functions**: Created reusable functions for consistent access control across the application

## Files Modified
1. `includes/access_control.php` - New file with access control functions
2. `admin/index.php` - Updated access control
3. `admin/users.php` - Updated access control
4. `admin/settings.php` - Updated access control
5. `teachers/dashboard.php` - Updated access control
6. `teachers/routine.php` - Updated access control

## Verification
The solution ensures that:
- Teachers can only access their designated pages (`teachers/dashboard.php`, `teachers/routine.php`, etc.)
- Teachers cannot access admin pages (`admin/*`)
- Admins can access all admin pages
- Students can only access their designated pages

This implementation fully addresses the requirement that "when teachers log in, they should not be able to access any other pages except their designated ones, meaning they cannot access admin pages."