新手分页有关问题，PHP分页代查询功能，没有查询结果就出错

 include("conn.php");

function pager($rows,$page_size){ 
global $page,$select_from,$select_limit,$pagenav; 
$page_count = ceil($rows/$page_size); 
if($page <= 1 || $page == '') $page = 1; 
if($page >= $page_count) $page = $page_count; 
$select_limit = $page_size; 
$select_from = ($page - 1) * $page_size.','; 
$pre_page = ($page == 1)? 1 : $page - 1; 
$next_page= ($page == $page_count)? $page_count : $page + 1 ; 
$pagenav .= "第 $page/$page_count 页 共 $rows 条记录 "; 
$pagenav .= "<a href='?page=1'>首页</a> "; 
$pagenav .= "<a href='?page=$pre_page'>前一页</a> "; 
$pagenav .= "<a href='?page=$next_page'>后一页</a> "; 
$pagenav .= "<a href='?page=$page_count'>末页</a>"; 
$pagenav.="　跳到<select name='topage' size='1' onchange='window.location=\"?page=\"+this.value'>\n"; 
for($i=1;$i<=$page_count;$i++){ 
if($i==$page) $pagenav.="<option value='$i' selected>$i</option>\n"; 
else $pagenav.="<option value='$i'>$i</option>\n"; 

} 
} 

///////////////////////////// 利用pager函数计算出 $select_from 从哪条记录开始检索、$pagenav 输出分页导航 
$countsql="select * from manager where 0=0";
  if ($_POST[chinaname]!=""){ 
      $countsql=$countsql." and chinaname like '%$_POST[chinaname]%'";
  }
  if ($_POST[Tel]!=""){ 
      $countsql=$countsql." and Tel like '%$_POST[Tel]%'";
  }
$rows = mysql_num_rows(mysql_query($countsql)); 
$page = $_GET['page'];
pager($rows,2); 
$sql = "select * from manager where 0=0"; 
  if ($_POST[chinaname]!=""){ 
  $sql=$sql." and chinaname like '%$_POST[chinaname]%'";
  }
  if ($_POST[Tel]!=""){ 
  $sql=$sql." and Tel like '%$_POST[Tel]%'";
  }
  $sql=$sql." limit $select_from $select_limit";
  
  echo $sql;
$rst = mysql_query($sql); 

while($row=mysql_fetch_array($rst)){