php分页代码实例有注释

<?php
    header("content-type:text/html;charset=utf-8");
    //数据库连接
    $conn = mysql_connect("localhost", "root", "111") or die("not connnected : ".mysql_error());
    mysql_select_db("test", $conn);
    mysql_query("set names utf8");
    //查询共有多少行数据
    $sql1 = "select count(*) from user";
    $ret1 = mysql_query($sql1);
    $row1 = mysql_fetch_row($ret1);
    $tot = $row1[0];
    //每页多少行数据
    $length = 5;     
    //总页数 
    $totpage = ceil($tot / $length);
    //当前页数
    $page = @$_GET['p'] ? $_GET['p'] : 1;
    //limit 下限
    $offset = ($page - 1) * $length;
    echo "<center>";
    echo "<h2>php padding</h2>";
    echo "<table width='700px' border='1px' >";
    echo "<tr>";
    echo "<th>ID</th>";
    echo "<th>USER</th>";
    echo "<th>PASS</th>";
    echo "</tr>";
    //将查询出来的数据用表格显示
    $sql2 = "select * from user order by id limit {$offset}, {$length}";
    $ret2 = mysql_query($sql2);
    while ($row2 = mysql_fetch_assoc($ret2)) {
        echo "<tr>";
        echo "<td>{$row2['id']}</td><td>{$row2['name']}</td><td>{$row2['pass']}</td>";
        echo "</tr>";
    }
    echo "</table>";
    //上一页和下一页
    $prevpage = $page - 1;
    if ($page >= $totpage) {
        $nextpage = $totpage;
    } else {
        $nextpage = $page + 1;
    }
    //跳转
    echo "<h3><a href='index.php?p={$prevpage}'>上一页</a>|<a href='index.php?p={$nextpage}'>下一页</a></h3>";
    echo "</center>";