php is already enabled from a fresh installation if you use EHCP Force Edition.
Login to the EHCP panel, select the domain that has been added to the panel that you want to customize, and then click on "Edit Apache2 Template". This is the domain specific template which can be modified to accomplish anything custom you might need (but you could end up breaking your web server if you use invalid syntax). If that happens, simply clear the contents of /var/www/new/ehcp/apachehcp.conf and restart the web server. Undo your breaking changes, and then resync the domains.
You should be using the panel to make any additions or customizations to any web server template. Thus, you would login to the panel at
http://localhost/ehcpI hope this helps.