# Column Rename: finish_date → end_date

## Overview
Renamed the `finish_date` column to `end_date` across the entire billing module for better semantic clarity. The column represents when a server's subscription ends/expires, so "end_date" is more descriptive.

## Files Modified

### Database Schema
1. **module.php** - Line 77
   - Updated schema definition: `finish_date` DATETIME NULL → `end_date` DATETIME NULL

2. **migration_to_invoices.sql**
   - Line 26: Updated AFTER clause in ADD COLUMN statement
   - Lines 49-60: Updated column conversion logic from VARCHAR to DATETIME
   - All references to the column name updated

### PHP Application Code
3. **cron-shop.php** (19 occurrences)
   - Lines 78-80: Updated query conditions checking end_date IS NOT NULL
   - Lines 97, 121, 124: Updated email notification date formatting
   - Lines 142, 150-151: Updated suspension query conditions
   - Lines 218, 226-227: Updated deletion query conditions
   - Lines 283, 288: Updated legacy code comments and queries
   - Lines 301, 304: Updated developer notes
   - Lines 336, 341: Updated suspension logic
   - Line 395: Updated final cleanup query

4. **cart.php** (14 occurrences)
   - Lines 89-106: Updated variable names from $finish_date to $end_date
   - Line 111: Updated column existence check
   - Lines 117, 119, 121, 127: Updated SQL UPDATE statements
   - Line 148-149: Updated audit logging

5. **my_account.php** (4 occurrences)
   - Line 128: Updated SELECT query field
   - Line 328: Updated display formatting (3 references in same line)

6. **my_servers.php** (2 occurrences)
   - Line 43: Updated SQL comment
   - Line 44: Updated column alias

7. **admin_invoices.php** (1 occurrence)
   - Line 99: Updated display column

8. **add_to_cart.php** (10 occurrences)
   - Lines 134-151: Updated variable names, column checks, INSERT queries, logging

9. **create_servers.php** (12 occurrences)
   - Line 244: Updated condition check
   - Lines 295-296: Updated comments
   - Lines 301-330: Updated variable names in date calculation logic
   - Line 342: Updated SET clause in UPDATE query (2 references)

10. **payment_success.php** (11 occurrences)
    - Lines 35-102: Updated all references in payment processing logic
    - Variable renamed: $finish_date_val → $end_date_val
    - Updated column existence checks and SQL generation

### Documentation
11. **INVOICE_SYSTEM.md** (6 occurrences)
    - Line 27: Updated field description
    - Line 67: Updated workflow documentation
    - Line 74: Updated renewal process
    - Line 84: Updated expiration logic
    - Line 113: Updated payment completion notes
    - Line 124: Updated My Account display notes

12. **MIGRATION_SUMMARY.md** (4 occurrences)
    - Line 11: Updated changelog entry
    - Line 18: Updated bug fix description
    - Lines 30, 36: Updated cron process descriptions
    - Line 87: Updated SQL schema example
    - Line 141: Updated verification notes

## Database Impact

### For Fresh Installations
- New installations will create the `ogp_billing_orders` table with `end_date` DATETIME NULL

### For Existing Installations
- Run the updated `migration_to_invoices.sql` script
- The script will handle the column rename automatically using dynamic SQL:
  ```sql
  -- Checks if column exists as 'finish_date' and renames to 'end_date'
  -- Then converts data type from VARCHAR to DATETIME
  ```

## Testing Checklist
- [x] Module schema updated (module.php)
- [x] Migration script updated (migration_to_invoices.sql)
- [x] All PHP files using the column updated
- [x] All SQL queries updated
- [x] All variable names updated
- [x] All comments and documentation updated
- [x] Verified no remaining `finish_date` references (except log files)

## Backwards Compatibility
⚠️ **BREAKING CHANGE**: This rename requires running the migration script on existing databases. 

**Migration Path:**
1. Backup database
2. Run updated `migration_to_invoices.sql`
3. The script will automatically rename `finish_date` to `end_date`
4. Verify column exists: `SHOW COLUMNS FROM ogp_billing_orders LIKE 'end_date';`

## Notes
- Log files may still contain old references to `finish_date` - this is expected and harmless
- The semantic meaning of the column is unchanged (server expiration date)
- All date calculations remain identical
- No functional changes, only naming improvement for clarity