PHP is a modular system where you can install and enable or disable its modules. These modules provide extra functionalities and you can enable the modules to access the said functionalities or you want to disable certain modules to enhance your website's performance and reduce your security vector.
Shared hosting system such as
cPanel doesn't let you install 3rd party
PHP modules yourself but it normally comes with most standard modules and you can enable or disable the modules from
Steps to enable and disable PHP modules in cPanel hosting:
Comment anonymously. Login not required.