PHP fórum

 <div class="col-md-8">            
                <?php
//This page display a topic
if(isset($_GET['id']))
{
    $id = intval($_GET['id']);
    $dn1 = mysql_fetch_array(mysql_query('select count(t.id) as nb1, t.title, t.message, t.parent, count(t2.id) as nb2, c.name from topics as t, topics as t2, categories as c where t.id="'.$id.'" and t.id2=1 and t2.id="'.$id.'" and c.id=t.parent group by t.id'));
if($dn1['nb1']>0)
{
?>
<?php
$dn2 = mysql_query('select t.id, t.title, t.authorid, u.nick as author, count(r.id) as replies from topics as t left join topics as r on r.parent="'.$id.'" and r.id=t.id and r.id2!=1  left join users as u on u.id=t.authorid where t.parent="'.$id.'" and t.id2=1 group by t.id order by t.timestamp2 desc');
while($dnn2 = mysql_fetch_array($dn2))
{
?>
                    <div class="panel panel-default"> 
                        <div class="panel-heading"> 
                            <h3 class="panel-title">Fórum &bull; <?php echo htmlentities($dn1['name'], ENT_QUOTES, 'UTF-8'); ?> &bull; <?php echo htmlentities($dn1['title'], ENT_QUOTES, 'UTF-8'); ?>  <?php
if(isset($_SESSION['user']))
{ ?> <a href="new_reply.php?id=<?php echo $id; ?>" class="btn btn-success pull-right">Nová odpověď</a> <?php } ?></h3>                         </div>                         
                        <div class="panel-body"> 

<?php echo $dn1['message']; ?>
<br><br>
<div class="panel-footer"> 
                            <i class="fas fa-calendar-alt"></i> <?php echo date('d.m.Y v H:i' ,$dnn2['timestamp2']); ?>
                            <i class="fa fa-user"></i> <a href="profile.php?id=<?php echo $dnn2['authorid']; ?>"><?php echo $dnn2['author']; ?></a>
                        </div> 
                    </div>
</div>
<?php
}}
else
{
    echo '<h2>This topic doesn\'t exist.</h2>';
}
}
else
{
    echo '<h2>The ID of this topic is not defined.</h2>';
}
?>        
                        
                        
</div>