Creating a module and need system calls

I like to create a PBillX module (Hospitality).
This i had already done with former freepbx versions, and it works fine.
But now there are changes which omit system calls (Asterisk user is now limited).
How i can system calls in the install.php to install the pbillx services?

Thanks for your suggestions

Fred Montero, PBillX Inc.

FreePBX bootstrap info here:

Sample module here: