Module MCP method only working with get, not post

Okay, so this is the first time i’ve written a module so probably a newb question here!

I’m slowly building up a module and one of the things it needs to be able to do is save settings.

So in my mcp file i have an ‘index’ method and a ‘save_settings’ method.

function save_settings()
    {
        error_log('save settings function');
        $this->EE->session->set_flashdata('message_success', $this->EE->lang->line('record_added'));
        $this->EE->functions->redirect(BASE.AMP.'C=addons_modules'.AMP.'M=show_module_cp'.AMP.'module=refer_a_friend');
    }

Right now, the save settings method doesn’t really do anything, it just flashes a success message and redirects to the module index page.

The thing is, it only words when I access it directly by typing in the method name in the browser address bar.

When I submit the form on the index page which calls it, I wind up at the control panel home page. When I take the form action attribute and paste it directly into the address bar, I get the desired action, so I know it’s not a problem with my form action attribute.

I have an error log in there, and I can see that it isn’t being processed at all when I submit my form.

I have looked at the apache log but no clue there… this is what happens:

127.0.0.1 - - [09/Sep/2011:15:34:25 -0700] "POST /system/index.php?S=fa1a9ef3d8437ec0d33da8e0012b2d37467291bb&D=cp&C=addons_modules&M=show_module_cp&module=refer_a_friend&method=save_settings HTTP/1.1" 302 20
127.0.0.1 - - [09/Sep/2011:15:34:25 -0700] "GET /system/index.php?S=fa1a9ef3d8437ec0d33da8e0012b2d37467291bb&D=cp HTTP/1.1" 302 20

But if I enter the URL (get) it goes where I expect it to

127.0.0.1 - - [09/Sep/2011:15:34:49 -0700] "GET /system/index.php?S=fa1a9ef3d8437ec0d33da8e0012b2d37467291bb&D=cp&C=addons_modules&M=show_module_cp&module=refer_a_friend&method=save_settings HTTP/1.1" 302 20
127.0.0.1 - - [09/Sep/2011:15:34:50 -0700] "GET /system/index.php?S=fa1a9ef3d8437ec0d33da8e0012b2d37467291bb&D=cp&C=addons_modules&M=show_module_cp&module=refer_a_friend HTTP/1.1" 200 13664

I’ve spent a couple of hours trying things here, including looking at other 3rd party modules, so any pointers greatly appreciated.