WHMPHP has a module for WHMCS billing system. By using this module ,the Master Reseller can automate the reseller account creation.

Download

Download the zip file from www.whmphp.com/download/whmcs.zip
Unzip and upload to /modules/servers/whmphp

Please refer the instruction file included in the zip file for more information on how to integrate it with your whmcs.