我有此功能可生成产品类别菜单。几周前，当我的类别较少时，它工作得很好，但每次添加新类别时，页面加载时间都会越来越长。这是功能：
function getProductCategorieshome(){
$query='select id, bg_category,url from products_categories
where visible="1" and parent="0" group by bg_category order by bg_category ASC';
$result=mysql_query($query) or die();
$num_rows=mysql_num_rows($result);
if($num_rows){
echo '<ul id="mmenu" class="top-level">';
$htm='';
for($i=0;$i<$num_rows;$i++){
$row=mysql_fetch_row($result);
//sub category
$query="select id,bg_category,parent,url from products_categories
where visible='1' and parent='".$row[0]."' group by bg_category order by bg_category ASC";
$result1=mysql_query($query) or die();
$num_rows1=mysql_num_rows($result1);
if($num_rows1>0){
$sub_htm='';
for($j=0;$j<$num_rows1;$j++){
$row1=mysql_fetch_row($result1);
//here I check if we have products associated with the category so not showing empty categories
$querys="select distinct pc.id, bg_category,url
from products_categories pc, products_to_categories ptc, products p
where pc.id IN(select id from products_categories where
visible='1' and parent='".$row1[0]."' group by bg_category order by bg_category ASC) and
pc.id=ptc.category_id and p.id=ptc.product_id and
p.id not in (".$_SESSION['expired_products'].")
group by bg_category order by bg_category ASC";
$result1s=mysql_query($querys) or die();
$num_rows1s=mysql_num_rows($result1s);
if($num_rows1s>0){
$sub_sub_htm='';
for($k=0;$k<$num_rows1s;$k++){
$row1s=mysql_fetch_row($result1s);
$sub_sub_htm.='<li class="li5">'.$row1s[1].'</li>';
}
if(!empty($sub_sub_htm)) $sub_htm.='<li class="li2">'.$row1[1].'<ul class="sub-level">
'.$sub_sub_htm.'</ul></li>';
}else{
$sub_htm.='<li>'.$row1[1].'</li>';
}
}
if(!empty($sub_htm)){
$htm.='<li class="li2">'.$row[1].'<ul class="sublevel">'.$sub_htm.'</ul></li>';
}
}else{
$htm.='<li class="li1">'.$row[1].'</li>';
}
}
echo $htm;
echo '</ul>';
}
}
我的产品类别表如下：
#id #bg_category #parent #url
1 phones 0 phones
2 smartphones 1 smartphones
3 Nokia 2 nokia
........... and so on
如何优化此功能。如果我不打电话给功能页面平均加载1秒。加载后，加载时间增加到4.5秒。我相信添加更多类别会增加加载时间问题。
很抱歉，如果我无法更好地格式化以下代码！