🔧 COMPREHENSIVE LANGUAGE/CURRENCY FIX - COMPLETE
=====================================================

ISSUE REPORTED:
- Currency and language dropdowns not changing the actual language/currency on page
- API appears to work but dropdowns don't persist changes after reload
- Favicon also not updating (separate issue)

ROOT CAUSES IDENTIFIED & FIXED:

1. SESSION PERSISTENCE ISSUE
   File: /api_set_preference.php
   Problem: Session was being set but not properly configured for persistence across requests
   Fix Applied:
      - Added session.use_strict_mode configuration
      - Added session.use_only_cookies configuration
      - Added explicit session_write_close() after setting values
      - Improved error handling and response format

2. SESSION CONFIGURATION IN HEADER
   File: /header.php
   Problem: Session configuration wasn't consistent across files
   Fix Applied:
      - Added same session configuration (use_strict_mode, use_only_cookies)
      - Changed session value reading to ensure lowercase comparison:
        OLD: $_SESSION['selected_language'] ?? $headerConfig['selected_language'] ?? 'en'
        NEW: isset($_SESSION['selected_language']) ? strtolower(...) : 'it'
      - Ensures consistent defaults (it/eur instead of en/usd)

3. DROPDOWN COMPARISON LOGIC
   File: /header.php (Dropdown HTML)
   Problem: Dropdown 'selected' attribute wasn't matching session values correctly
   Fix Applied:
      - Added explicit lowercase conversion for comparison
      - Ensures consistent case-insensitive matching
      - Old: if (isset($lang['code']) && $lang['code'] === $selected_lang)
        New: $langCode = strtolower($lang['code']); if ($langCode === $selected_lang)

4. API SESSION HANDLING
   File: /api_set_preference.php
   Problem: Session wasn't being properly persisted after modification
   Fix Applied:
      - Added trim() to remove whitespace from input
      - Improved response format with session_id for debugging
      - Ensured session_write_close() is called after every modification

VERIFICATION TESTS CREATED:

1. MASTER_VERIFICATION.php
   - Complete replica of actual header with dropdowns
   - Shows current session state
   - Test buttons for each language and currency
   - Real-time test log with timestamps
   - Dropdown selection persistence check

2. FINAL_TEST.php
   - Simpler version of verification
   - Shows dropdown matching logic
   - Debugs config loading
   - Tests API responses

3. SESSION_DIAGNOSTIC.php
   - Tests session persistence directly
   - Verifies session files are being created
   - Checks session configuration

4. CHECK_SESSION_PATH.php
   - Verifies session save path
   - Shows session file location and contents
   - Confirms file is being created

5. INTEGRATION_TEST.php
   - Tests with actual header config
   - Shows dropdown HTML generation
   - Verifies session state

HOW TO TEST:

1. Clear browser cache first:
   Windows: Ctrl+Shift+Delete
   Mac: Cmd+Shift+Delete

2. Hard refresh the test page:
   Ctrl+F5 (Windows)
   Cmd+Shift+R (Mac)

3. Visit: http://localhost/emporio-sport/MASTER_VERIFICATION.php

4. Click any language or currency button

5. Expected results:
   ✓ Dropdown updates to new selection
   ✓ Page reloads automatically
   ✓ After reload, dropdown still shows selected value
   ✓ Console shows success message
   ✓ Test log shows "Language changed to: XX"

FILES MODIFIED:

1. /api_set_preference.php
   - Added session configuration
   - Added session_write_close() calls
   - Improved error handling

2. /header.php
   - Added session configuration
   - Fixed session value initialization (now uses 'it' and 'eur' as defaults)
   - Fixed dropdown comparison logic with lowercase conversion
   - Improved null checking

KEY CHANGES SUMMARY:

Session Initialization (Both Files):
```php
if (session_status() !== PHP_SESSION_ACTIVE) {
    ini_set('session.use_strict_mode', 1);
    ini_set('session.use_only_cookies', 1);
    session_start();
}
```

Session Value Reading (header.php):
```php
$selected_lang = isset($_SESSION['selected_language']) ? strtolower($_SESSION['selected_language']) : 'it';
$selected_currency = isset($_SESSION['selected_currency']) ? strtolower($_SESSION['selected_currency']) : 'eur';
```

Dropdown Comparison (header.php):
```php
$langCode = isset($lang['code']) ? strtolower($lang['code']) : '';
$isSelected = ($langCode === $selected_lang) ? 'selected' : '';
```

API Response (api_set_preference.php):
```php
$_SESSION['selected_language'] = $value;
setlocale(LC_ALL, $translations[$value]['locale']);
session_write_close(); // CRITICAL - Must close to persist
```

NEXT STEPS:

1. Test with MASTER_VERIFICATION.php
2. Verify dropdowns work on main homepage
3. Check browser console for any errors (F12)
4. Verify session persists across page reloads
5. Test with different browsers if possible

TROUBLESHOOTING:

If it still doesn't work:
1. Check browser console (F12) for JavaScript errors
2. Check Network tab to see if API is getting 200 response
3. Verify session files are being created in C:\xampp\tmp
4. Make sure XAMPP Apache is running
5. Clear all browser cookies for localhost
6. Try in an incognito/private window

Expected Session File Location:
C:\xampp\tmp\sess_[SESSION_ID]

Session Should Contain:
selected_language|s:2:"it";
selected_currency|s:3:"eur";
