Error "Class not found" after updating OpenCart 4

Question

After updating to the latest OC4 version, got an error:

```
Fatal error: Class 'Opencart\System\Engine\Controller' not found
```

Cache cleared, permissions checked. What could it be?

Олексій Коваленко · Accepted Answer

Here's a solution that works for me in production:

**Step 1:** Check PHP version
```bash
php -v
# Need 8.0 or higher
```

**Step 2:** Clear cache completely
```bash
rm -rf storage/cache/*
rm -rf system/storage/cache/*
```

**Step 3:** Check permissions
```bash
chmod -R 755 storage/
chmod -R 755 system/storage/
```

**Step 4:** Check namespace in controller
```php
namespace Opencart\Admin\Controller\Module;
// Must match the file path
```

After these steps, the problem usually resolves!

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