$oncekikayit = $db->query("SELECT * FROM haber WHERE id < $id ORDER BY id DESC LIMIT 1");
$onceki = $oncekikayit->fetch();
$sonrakikayit = $db->query("SELECT * FROM haber WHERE id > $id ORDER BY id ASC LIMIT 1");
$sonraki = $sonrakikayit->fetch();

<?php echo $oncekikayit ['SeoUrl']; ?>

<?php echo $sonrakikayit ['SeoUrl']; ?>