php分页

<?php
    header("content-type:text/html;charset=utf-8");
    mysql_connect("127.0.0.1","root","") or die("连接失败");//连库
    mysql_select_db("demo");
    mysql_query("set names utf-8");
    $sql = "select * from user";
    $res = mysql_query($sql);
    $count = mysql_num_rows($res);//表中数据总数
    $size = 4;//每页显示的条数
    $page = isset($_GET['page'])?$_GET['page']:1;//当前页
    if($page-1<=1){
        $last = 1;
    }else{
        $last = $page-1;
    }
    //$down = $page+1;//下一页
    $last = ceil($count/$size);//尾页
    $offset = ($page-1)*$size;//偏移量（开始位置）
    $sql = "select * from user limit $offset,$size";  //第一页  从0    4条//4    4
    $res = mysql_query($sql);
    $arr = "";
    while($data = mysql_fetch_assoc($res)){
        $arr[] = $data;
    }
?>
<table border="1">
    <tr>
        <td>ID</td>
        <td>用户名</td>
        <td>手机号</td>
    </tr>
    <?php
        foreach($arr as $v){ ?>
            <tr>
                <td><?php echo $v['user_id']?></td>
                <td><?php echo $v['user_name']?></td>
                <td><?php echo $v['tel']?></td>
            </tr>
    <?php } ?>
</table>

<a href="show.php?page=1">首页</a>
<?php
    if($page>1){?>
        <a href="show.php?page=<?php echo $up ?>">上一页</a>
  <?php  } ?>
<?php
    for($i=1;$i<=$last;$i++){ ?>
        <a href="show.php?page=<?php echo $i?>"><?php echo $i?></a>
    <?php } ?>
<?php
if($page<$last){?>
    <a href="show.php?page=<?php echo $down ?>">下一页</a>
<?php  } ?>
<a href="show.php?page=<?php echo $last ?>">尾页</a>