Our WHM/CPanel installation is using CloudLinux. It is a Linux distribution that isolates one user from the other in terms of security (filesystem access, etc) and resources (PHP, RAM, etc). Under CloudLinux the PHP version is handled in CPanel in the Software > Select PHP version section:
There you can select the desired PHP version (should be 7+ nowadays):
And the desired PHP modules (do not forget to check MySQL):
On the top left you can choose Switch to PHP Options and set the desired resource limits, like RAM memory limit, max execution time, max input vars, post max size, upload max file size:
