To enable optional PHP extensions on your Managed Cloud Server:
- Access Managed Cloud Platform: First, log in to the platform.
- Navigate to Your Website: Select 'Websites' from the left navigation bar and then click on the specific website you wish to update.
- Change PHP Version: Go to 'Advanced' > 'Developer tools'. Here, in the PHP section, use the checkbox under "PHP extensions" to select the PHP extensions you prefer.
This process enables you to enable optional PHP extensions in addition to the default extensions which are out of the box.