为什么上一页到第一页之后还可以上一页到-1？？
<html>
<head>
<meta http-equiv="Content-type" content="text/html;charset=utf-8">
</head>
<style>
body{
font-size: 12px;font-family:verdana;width:100%;
}
div.page{
text-align: center;
}
div.content{
height:300px;
}
div.page a{
border:#ff3333 1pxsolid;text-decoration:none;padding: 2px 5px 2px 5px;margin: 2px;
}
div.page span.current{
border:#000099 1px solid;background-color:#000099;padding:1px 1px 1px 1px;margin:2px;
}
div.page span.disable{
border:#eee 1px solid;padding:1px 1px 1px 1px;margin:2px;color:#ddd;
}
div.page form{
display:inline;
}
</style>
<body>
<?php
/**1.传入页码**/
$page = $_GET['p'];
/**2根据页码取出数据：PHP->mysql处理**/
$host = "localhost";
$username = "root";
$password = "root";
$db = "shop";
$pageSize = 5;
$showPage = 5;
//链接数据库
$conn = mysql_connect($host,$username,$password);
if(!$conn){
echo '数据库连接失败';
exit;
}
//选择要操作的数据库
mysql_select_db($db);
//设置数据库编码格式
mysql_query("set names utf8");
//编写SQL获取分页数据SELECT * FROM 表明 LIMIT 起始位置，显示条数
$sql="select * from sw_goods limit ".($page-1)*$pageSize.",$pageSize";
//把sql语句传送到数据库
$result = mysql_query($sql);
// var_dump($result);
//处理我们的数据
echo "<div class=''content>";
echo'<table border=1 cellspacing=0 width=40% align=center>';
echo '<tr><td>ID</td><td>NAME</td></tr>';
while($row = mysql_fetch_assoc($result)){
echo '<tr>';
echo "<td>{$row['goods_id']}</td>";
echo "<td>{$row['goods_name']}</td>";
echo '</tr>';
}
echo'</table>';
echo '</div>';
// 释放结果集，关闭连接
mysql_free_result($result);
//获取数据库总数
$total_sql = "SELECT COUNT(*)FROM sw_goods";
$total_result = mysql_fetch_array(mysql_query($total_sql));
$total = $total_result[0];
//计算页数
$total_pages = ceil($total/$pageSize);
//mysql_close($conn);
/**3显示数据+分页条**/
$page_banner = "<div class='page'>";
//计算偏移量
$pageoffset = ($showPage-1)/2;
if($page > 1){
$page_banner .= "<a href= '".$_SERVER['PHP_SELF']."?p=1'><首页</a>";
$page_banner .= "<a href= '".$_SERVER['PHP_SELF']."?p=".($page-1)."'>上一页</a>";
}else{
$page_banner.= "<span class='disable'>首页</a></span>";
$page_banner.= "<span class='disable'>上一页</a></span>";
}
//初始化数据
$start = 1;
$end = $total_pages;
if($total_pages > $showPage){
if($page > $pageoffset + 1){
$page_banner .= "...";
}
}
if($page < $pageoffset){
$start = $page - $pageoffset;
$end = $total_pages > $page+$pageoffset?$page+$pageoffset:$total_pages;
}else{
$start = 1;
$end = $total_pages > $showPage?$showPage:$total_pages;
}
if($page+$pageoffset>$total_pages){
$start = $start-($page + $pageoffset - $end);
}
for($i = $start;$i<=$end;$i++){
if($page == $i){
$page_banner .= "<span class='current'>{$i}</span>";
}else{
$page_banner .= "<a href='".$_SERVER['PHP_SELF']."?p=".$i."'>{$i}</a>";
}
}
//尾部省略
if($total_pages>$showPage && $total_pages>$page + $pageoffset){
$page_banner .= "...";
}
if($page < $total_pages){
$page_banner .= "<a href='".$_SERVER['PHP_SELF']."?p=".($page+1)."'>下一页</a>";
$page_banner .= "<a href= '".$_SERVER['PHP_SELF']."?p=".($total_pages)."'>尾页></a>";
}else{
$page_banner.= "<span class='disable'>下一页</a></span>";
$page_banner.= "<span class='disable'>尾页</a></span>";
}
$page_banner .="共{$total_pages}页.";
$page_banner .= "<form action='page.php' method='get'>";
$page_banner .= "到第<input type='text' size='2' name='p'>页";
$page_banner .= "<input type='submit' value='确定'>";
$page_banner .= "</form></div>";
echo $page_banner;
?>
</body>
</html>
