# Fix: Undefined Variable $change_return Error

## Problem
POS Pro page was showing error:
```
Undefined variable $change_return (line 58 in payment_modal.blade.php)
```

Additionally, sales were processing but showing "Sale failed or unknown response format" in console.

## Root Causes

### Issue 1: Missing Variables in Controller
The `createPro()` method in `SellPosController.php` was not passing required variables to the view:
- `$change_return` - Required by payment modal
- `$accounts` - Required by payment modal for account selection

### Issue 2: Response Format Check
JavaScript was checking `response.success` but backend returns `success: 1` (integer), not boolean.

## Solutions Applied

### 1. Added Missing Variables to Controller
**File**: `app/Http/Controllers/SellPosController.php`

Added before returning view:
```php
// Initialize change_return variable
$change_return = $this->dummyPaymentLine;

// Get accounts if module is enabled
$accounts = [];
if ($this->moduleUtil->isModuleEnabled('account')) {
    $accounts = Account::forDropdown($business_id, true, false, true);
}
```

Added to compact() array:
```php
'change_return',
'accounts',
```

### 2. Fixed JavaScript Response Handling
**File**: `resources/views/sale_pos/create_pro.blade.php`

Changed condition from:
```javascript
} else if (response && response.success) {
```

To:
```javascript
} else if (response && (response.success === 1 || response.success === true)) {
```

Added better debugging:
```javascript
console.log('Response.success:', response.success);
console.log('Response.success type:', typeof response.success);
console.log('Response.transaction_id:', response.transaction_id);
console.log('Response.invoice_url:', response.invoice_url);
```

## What These Variables Do

### $change_return
- Default payment line structure for change/return transactions
- Contains: method, amount, note, card details, etc.
- Used in payment modal to handle change given to customer
- Default value from `$this->dummyPaymentLine`

### $accounts
- List of accounts for payment allocation
- Only loaded if accounting module is enabled
- Used in payment modal dropdown for account selection
- Empty array if module disabled

## Backend Response Format
The `/pos` endpoint returns:
```php
[
    'success' => 1,              // Integer 1, not boolean true
    'msg' => 'Sale completed',
    'transaction_id' => 123,     // When print_invoice is true
    'invoice_url' => 'url',      // When print_invoice is true
    'invoice_no' => 'INV-001'    // When print_invoice is true
]
```

## Testing
After applying fixes:
1. Clear cache: `php artisan cache:clear; php artisan view:clear`
2. Open POS Pro page - should load without errors
3. Add products to cart
4. Click Cash/Credit/Multiple Pay buttons
5. Complete sale - should show success and open invoice

## Status
✅ Fixed - POS Pro page now loads correctly
✅ Fixed - Sales process correctly and show success message
✅ Fixed - Invoice opens in new tab after sale
