By default, the buildpack installs the cli module when you push a standalone application, and it installs the fpm module when you run a web application. You must specify cgi and pear if you want them installed following the below guide.
In the root folder of your application create a folder with name .bp-config. Under this folder create a file with name options.json
The below example shows an example PHP app directory after you create the .bp-config/options.json file.
You can explicitly enable any or all of: fpm, cli, cgi, and pear in your options.json file under the PHP_MODULES field.