php+mysql分页代码详解

<?php    
$perpagenum = 10;//定义每页显示几条    
$total = mysql_fetch_array(mysql_query("select count(*) from a"));//查询数据库中一共有多少条数据    
$Total = $total[0];                          //    
$Totalpage = ceil($Total/$perpagenum);//上舍，取整    
if(!isset($_GET['page'])||!intval($_GET['page'])||$_GET['page']>$Totalpage)//page可能的四种状态    
{    
    $page=1;    
}    
else    
{    
    $page=$_GET['page'];//如果不满足以上四种情况，则page的值为$_GET['page']    
}    
$startnum     = ($page-1)*$perpagenum;//开始条数    
$sql = "select * from a order by id limit $startnum,$perpagenum";//查询出所需要的条数    
echo $sql."    
";    
$rs = mysql_query($sql);    
$contents = mysql_fetch_array($rs);    
if($total)如果$total不为空则执行以下语句    
{    
    do    
    {    
    $id = $contents['id'];    
    $name = $contents['name'];    
    ?>    
    <table border="0" align="center">    
    <tr>    
    <td>id:    
    <?php echo $id;?>    
    </td>    
    </tr>    
    <tr>    
    <td>name:    
    <?php echo $name;?>    
    </td>    
    </tr>    
    </table>    
    <?php    
    }    
while($contents = mysql_fetch_array($rs));//do....while    
$per = $page - 1;//上一页    
$next = $page + 1;//下一页    
echo "<center>共有".$Total."条记录,每页".$perpagenum."条,共".$Totalpage."页 ";    
if($page != 1)    
{    
echo "<a href='".$_SERVER['PHP_SELF']."'>首页</a>";    
echo "<a href='".$_SERVER['PHP_SELF'].'?page='.$per."'> 上一页</a>";    
}    
if($page != $Totalpage)    
{    
echo "<a href='".$_SERVER['PHP_SELF'].'?page='.$next."'> 下一页</a>";    
echo "<a href='".$_SERVER['PHP_SELF'].'?page='.$Totalpage."'> 尾页</a></center>";    
}    
}    
else如果$total为空则输出No message    
{    
echo "<center>No message</center>";    
}    
?>