На что именно ругается и как устранить?

Fatal error: Call to a member function query() on null in /blabla/bloblo/public_html/bloblo/foot.php on line 1

$res = $db->query("SELECT * FROM `rek` where `date_last`>'".time()."' ORDER BY RAND() DESC LIMIT 6");

while ($row = $res->fetch_assoc()){
       if($row['color']==null){$name=' '.htmlspecialchars($row['name']);}else{$name='<font color="'.htmlspecialchars($row['color']).'"> '.htmlspecialchars($row['name']).'</font>';}
       if(abs(intval($row['bold']))==1){$nam='<b>'.$name.'</b>';}else{$nam=$name;}
       echo '<div class="footer"><center><img src="http://www.google.com/s2/favicons?domain='.htmlspecialchars($row['url']).'"><a class="title" href='.htmlspecialchars($row['url']).'>'.$nam.'</a></center></div>';
}