Your Hosting Account's PHP extensions and options can be managed at any time. In order to do that, simply open Websites → Manage, search for PHP Configuration on the sidebar and click on it:
On the newly opened page, select the tab for what you would like to manage - PHP extensions or PHP options:
PHP extensions
At the top of the page, you will see a list of the Built-in Extensions, which come with your current PHP version. They cannot be disabled. Below, you will see the list of all the installed extensions, and be able to manage them depending on your needs:
NOTES:
The list you see will always differ based on the chosen PHP version
After applying changes, remember to save them by clicking on Save at the bottom of the page
If you would like to set all the values to default, just click on Reset, which can be found at the bottom of the page:
PHP options
At the top of the page, you will see a list of basic options, which you can manage by adding/removing a checkbox:
Below, you will find parameters, which you can edit, the list of disabled functions, change the value of some limits (by default, they are already set to the maximum value available for your hosting plan), and many more.
Additional resources: