Trying to make php elseif post condition but not working

I'm trying to make some php else if but seems to have some trouble making post method work. Here's the condition:

        <?php if (!$yes_good) { ?>

        <form action='/' method='post'>

          <input type="hidden" name="GOOD" value="1" />

          <input id="linkid" class="label" type="submit" value="" name='' />

        </form>


    <?php } else { ?>

        <form action='/' method='post'>  

          <input type="hidden" name="BAD" value="1" />

          <input id="linkid" class="label" type="submit" value="" name='' />

        </form>


        <?php
    }
    ?>

Result page:

    <?php if (isset($_POST['GOOD'])): ?>

  <h1> GOOD! </h1>

<?php elseif (isset($_POST['BAD'])): ?>

 <h1> BAD! </h1>

<?php else: ?>

 <!-- Shows up when form is bypass or page is access directly. -->
 <h1> Not GOOD or BAD </h1> 


<?php endif; ?>

The php elseif post method seems not working.