Two login forms on a same page (user/login) I've used hook_form_FORM_ID_alter() to alter the user/login form.
Now I have to create another form that will have different submit handler because will be connecting with web service.

The hook_form_FORM_ID_alter() is altering the existing default login form and cannot create another form. 
We have sellers and customers users.

The reason for creating 2 forms is: On the first form the submit handler is connecting with the web service for the customers method and the submit handler of the second one it should connect with the method web service for the sellers. 
Is it possible to do this?
Here are some quick thoughts that should help you thinking.

I'm not sure yet if it's the best option (have to think about it for a while and I don't know all your details) but:


Create a new page via custom module, say /login.
Implement hook_page_alter() in the custom module and redirect all requests from /user/login to /login. Simply by:

if (arg(0) == 'user' &amp;&amp; arg(1) == 'login') {
  drupal_goto('login');
}

Create an alternate login form through your custom module with different submit handlers etc.
On /login page, create any markup you need and pass the two forms. First form will be the regular drupal login form (you can get it by drupal_get_form('user_login')) and the second one will be the one you created manually. This way you have 2 login forms on the same screen with different submit handlers.


Check out user_login() function in the user.module file. That is the function that creates the login form.

Important: I didn't test this. Check it in and out to make sure there are no conflicts with other modules or workflows.

Hope this makes sense!