Question

How I can open a new tab in a Firefox add-on with POST variables?

For example, open http://localhost/ with these post variables:

a=NOMADE
b=NOWAY
another=IDONTKNOW

Answer 1

The gBrowser.addTab function is what you want. One of the parameters you pass to that function is postData, and allows you to set the postData as you would like it. The MDN documentation for that function also points to an article on pre-processing POST data. If I read that second article correctly, the POST data needs to be passed in the form of an nsIInputStream (specifically created as nsIMIMEInputStream). The article provides a sample code snippet for converting from a standard GET style format string (example: foo=1&goo=somestring) to the intended format.

Edit: So, to use your example, you might do something like this:

var myData = "a=NOMADE&b=NOWAY&another=IDONTKNOW";

// TODO: Translate myData into the nsIMIMEInputStream format using the example
// from the second linked article above

// Add the tab, with the variable data
gBrowser.addTab("http://www.example.com/", {postData: myData});