Passing $params to custom page

[Bweb]

Here is what I cannot figure out:

 

I have created a custom form in the client area, where I want users to fill out some information and then use CURL to send it to an external system...

 

Used the guide here http://wiki.whmcs.com/Creating_Pages

 

...and in the "put any code you like", I was hoping to get the input from my .tpl file and place my custom code.

 

How can I pass the POST data from the tpl file into here? I started with:

if ($_POST["submit"])

..... Do all my CURL stuff here....

 

However, I also want to get some things from WHMCS, like the customers currency or name and add it to my Curl request...

 

 

Since most of the code is encrypted, how do the other pages pass information? For example, the "Update my profile" page would be good to have as an example since it pre-populates the fields from the DB, then allows me to change the info...