Native Installers for Bitnami Stacks are completely self-contained and run independently of the rest of the software or libraries installed on your system. This means that you shouldn't use the PHP installation of your system but the PHP shipped by the installer itself.
In order to do that, we have a utility named Bitnami console which loads all necessary ENV vars needed to run correctly any command using the Bitnami Stack components.
To enter the Bitnami console just execute:
Then, you should be able to run
Hope it helps,