php分页问题 系统提示未定义变量Undefined variable: php_self
这个页面是一个可以正常显示列表的页面，单击“下一页”时，页数会发生变化，但是页面内容还是显示的第一页。系统提示第72和79行未定义变量Undefined variable: php_self 我应该怎样修改下？
<?php
/*error_reporting(E_ALL ^ E_NOTICE);*/
//######################课题列表##########################
include "config.php";
include "header.php";
?>
<meta http-equiv="Content-Type" content="text/html; charset=GB2312">
<link href="style.css" rel="stylesheet" type="text/css">
<title>课题列表</title>
<style type="text/css">
<!--
.STYLE1 {font-size: 14px}
-->
</style>
<table width="740" border="0" cellspacing="1" cellpadding="0" bgcolor="#333333" align="center">
<tr>
<td width="60" height="30" bgcolor="#FFFFFF"> <div align="center" class="text"> <p class="STYLE1">课题编号</p></div> </td>
<td width="300" height="30" bgcolor="#FFFFFF"> <div align="center" class="title STYLE1">课题名称</div> </td>
<td width="85" height="30" bgcolor="#FFFFFF"> <div align="center" class="STYLE1">指导教师</div></td>
<td width="60" height="30" bgcolor="#FFFFFF"> <div align="center" class="STYLE1">职称</div> </td>
<td width="60" height="30" bgcolor="#FFFFFF"> <div align="center" class="title STYLE1">可选人数</div> </td>
<td width="80" height="30" bgcolor="#FFFFFF" class="title"><div align="center" class="STYLE1">选题情况</div> </td>
<td width="60" height="30" bgcolor="#FFFFFF" class="title"><div align="center" class="STYLE1">状态</div> </td>
<td width="60" height="30" bgcolor="#FFFFFF" class="title"><div align="center" class="STYLE1">详细资料</div> </td>
</tr>
<?php
$n=0;
$query=mysql_query("select count(*) as sm from jiaoshi");
mysql_query("set names 'GB2312'");
$row=mysql_fetch_array($query);
$count=$row['sm'];
if(empty($offset))
{$offset=0;}
echo $offset;
$query=mysql_query("select * from jiaoshi order by id asc limit $offset,$list_num") or die ("fail");
mysql_query("set names 'GB2312'");
while($row=mysql_fetch_array($query)){
if(($n%2)!='0'){
echo "<tr bgcolor=#ffffff>";}
else{
echo "<tr bgcolor=#E4E4E4>";
}
if($row['surplus']==0)
$ss="不可选";
else $ss="可选";
echo"
<td height='22' class='STYLE1'> <div align='center'>".$row['id']."</div></td>
<td height='22' class='STYLE1'> <div align='center'>".$row['subject']."</div></td>
<td height='22' class='STYLE1'> <div align='center'>".$row['teacher']."</div></td>
<td height='22' class='STYLE1'> <div align='center'>".$row['zhicheng']."</div></td>
<td height='22' class='STYLE1'> <div align='center'>".$row['number']."</div></td>
<td height='22' class='STYLE1'> <div align='center'>".$row['xuehao']."</div></td>
<td height='22' class='STYLE1'> <div align='center'>".$ss."</div></td>
<td height='22' class='STYLE1'> <div align='center'> <a href=xiangxiziliao.php?id=".$row['id'].">查看</a></div></td>
</tr> ";
$n++;
}
?></table>
<?php
extract($_REQUEST);
$pages=ceil($count/$list_num);
echo "<table width=760 border=0 cellspacing=0 cellpadding=0 align=center class='text'>
<tbody>
<tr>
<td width='159'><font color='#ff0000'>目前共有".$count."条记录</font> </td>
<td width='205'>".$pages."页</td>";
if($offset){
$preoffset=$offset-$list_num;
print "<td width='132'><a href="$php_self?offset=$preoffset">上一页</a></td>";}
else {
echo "<td width='132'>上一页</td>";
}
$newoffset=$offset+$list_num;
if(($pages!=0)&&(($newoffset/$list_num)!=$pages))
{
print("<td width='158'><a href="$php_self?offset=$newoffset">下一页</a></td>");
}
else{ echo "<td width='158'>下一页</td>";}
$pageno=($offset/$list_num)+1;
echo "<td width='112' class=text>第<input class=text type='text' size='4'value=".$pageno." readonly>
页</td>
<td width='4'> </td></tr>
</table>";
?>
<p>
</p>
<?php include "foot.php";?>
