custom "register" button on a form - problem with redirection
Use below code to achieve the same functionality.

function mymodule_form_user_login_block_alter(&amp;$form, $form_state, $form_id) {
  $form['actions']['register'] = array(
    '#markup' =&gt; l('Register', 'user/register'),
  );
}


Theme it using css to look like a button. Done !