<div id='mainpart'>
  <?php 
    if($msg):
      echo $msg['title'];
      echo '<br />';
      echo $msg['body'];
      if(!isset($_SESSION['zalogowany'])):
        $disabled = 'disabled="disabled"';
      else:
        $disabled = '';
      endif;
   ?>
   <div>
    <form action="index.php" method="post">
      <input type="submit" value="Usu wiadomo"
        <?php echo $disabled; ?>>
      <input type="hidden" name="action" value="deletemsg">
      <input type="hidden" name="id" value="<?php echo $msg['id']; ?>">
    </form>
  </div>
   <?php
    else:
      echo 'Nie ma nic do wywietlenia.';
    endif;
  ?>
</div>