You are closing an <a> tag that is not opened:
if ($mainnav7[$b] == "title") {
echo "<div class=\"menutitle\">$mainnav5[$b]
</a></div>";
I know that is not causing your problem but it's all I could find wrong with the code... everything else seems ok.
I am not a PHP expert by any means though... I am sure there are others here who may be of more assistance.
Best of Luck
Mike.
Not Just Graphics.