WordPress – Plugin – Admin – Post Back

I am writing a plugin which adds an options page beneath the “Media” menu.

The majority of my custom page seems to work fine, with the exception that my submit form shows an error page.

How do I intercept the postback?

<form id="special-form" action="upload.php?page=special-page" method="get">

...

<div class="tablenav">
   <div class="alignleft actions">
      <select name="action">
         <option value="-1" selected="selected">Bulk Actions</option>
      <?php if ($is_active) : ?>
         <option value="trash">Move to Trash</option>
      <?php elseif ($is_trash) : ?>
         <option value="restore">Restore</option>
         <option value="delete">Delete Permanently</option>
      <?php endif; ?>
      </select>

      <input type="submit" value="Apply" name="doaction" id="doaction" class="button-secondary action" />

      <?php wp_nonce_field('special-page'); ?>