PHP is a modular system where you can install and enable new modules to provide extra functionalities. These modules or extensions can also be disabled to enhance PHP's performance and reduce your security vector.
Shared hosting system such as cPanel doesn't let you install third party PHP extensions yourself but it normally comes pre-installed with most standard extensions. You can enable or disable these PHP modules on cPanel from the dashboard.
Modules are enabled and disabled only for the selected version. You'll need to enable or disable the PHP modules again if you switch to another PHP version later.
Modules are immediately enabled or disabled when checkbox is ticked or unticked.
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