The PHP configuration can only be modified when you are running your own custom version of PHP. We do not allow customers to change the shared PHP server configuration.
To begin using a custom version of PHP, please see the following knowledge base article. Once configured for custom PHP;
1. Go back to "Select a PHP version" within cPanel;
2. Select "Switch to PHP settings";
3. Click on an appropriate value to change these settings. When finished, click save;