Clients can independently change the PHP version for their hosting account.
You can also manage PHP modules and features, and include those that are needed for your site.

To change the PHP version, go to the cPanel control panel.

Find the "Select PHP Version" item and there you can select the desired PHP version and enable/disable the necessary modules.

If you do not have the "Select PHP Version" option in cPanel (or it is not activated)

That means you have another similar module: "MultiPHP Manager"
Select the site for which you want to make changes, select the desired PHP version,
Save the changes.

After that, you can make changes in the pcp settings (php.ini file)
This is done in the "MultiPHP INI Editor".
Settings can be changed for each site, each version of PCP.