title: Wordpress add_submenu_page won't accept parameters
body: <p>I've got this problem while developing a Wordpress plugin. Here's the code snippet of the area I'm working with:</p>
  
  <pre><code>add_submenu_page( 'admin_manager',
                    'Add Event',
                    'Add Event',
                    'manage_options',
                    'add_event&amp;action=modify',
                    'add_event_handler' );
  </code></pre>
  
  <p>As you can see, on my menu slug I want to add the '&amp;action=modify'</p>
  
  <pre><code>'add_event&amp;action=modify'
  </code></pre>
  
  <p>But when I do that, Wordpress denies me access and says I don't have the proper privileges. It works fine without the extra parameters, is there something built into wordpress that doesn't allow for such things?</p>
  
  <p>Any thoughts or workarounds?</p>