mysql分页类
class show_page
{
var $first;
var $prev;
var $next;
var $last;
var $sql;

//var $pages;

function show_page()
{
$this->first=1;
}

function setPage($total,$pagesize,$page)
{
global $producttable;
echo "pagesize=".$pagesize;
if ($total)
{
if ($total<$pagesize)
{
$pages=1;
}
if ($total%$pagesize)
{
$pages=ceil($total/$pagesize);
}
else
{
$pages=$total/$pagesize;
}
}

if(!isset($page))
$page=1;
if (isset($ys))
{
if ($ys>$pages)
$page=$pages;
else
$page=$ys;
}
$offset=($page-1)*$pagesize;

if($_GET[cateid]) {
$istype="where cateid=$_GET[cateid]";
}
if($_GET[sortid]) {
$istype="where sortid=$_GET[sortid]";
}
if(!$_GET[cateid]&&!$_GET[sortid]){
$istype="";
}
$sqlnum="select count(*) as num from $producttable $istype";
$sql="select * from $producttable $istype order by productid desc limit $offset,$pagesize";
#计算首页、上一页、下一页、尾页的页数值
$this->first=1;
$this->pages=$pages;
$this->prev=$page-1;
$this->next=$page+1;
$this->last=$pages;
$this->sqlnum=$sqlnum;
$this->sql=$sql;

}

}
$show_page = new show_page();
$show_page->setPage($total,$pagesize=2,$_GET[page]);

echo $show_page->sqlnum; 可以得到正确值
echo $show_page->sql; 可以得到正确值

echo $show_page->prev；得不到值
echo $show_page->pages；得不到值
echo $show_page->last；得不到值
是怎么回事啊