In cPanel hosting environments with CloudLinux, the operating system is providing caged environments (LVE) where by each individual site can have specific PHP versions and PHP extensions. In cases whereby you have CloudLinux, you can use PHP Selector to choose which version of PHP a site is operating under, and which PHP modules you want to use along with it.
First you need to login to WHM, and login to the cPanel for the associated account you want to change the PHP version for:
Once inside, you need to scroll down to the "Software" heading, and click on "Select PHP Version":
You may see something like this:
This means the site is currently running on the default cPanel supplied server-wide version of PHP, in this case it's PHP 5.6. The Native version of PHP will use the PHP modules set in EasyApache.
You can use the drop down menu to select an alternative, CloudLinux supplied version of PHP, and it's modules:
Use the drop down menu to select the PHP version, and set it using "Set as current", then tick the PHP modules that you want to be available to this site and then click "Save"
You can switch between different versions of the CloudLinux supplied PHP, or go back to the "Native" version if necessary.
If you have any issues or difficulty, please contact support for further assistance.
If you don't have CloudLinux, please see this article: How To Change Site PHP Version using cPanel (MultiPHP)