PHP Paging related issues system hints undefined variable undefined variable:php_self

PHP paging problem system hints undefined variable undefined variable:php_self
This page is a page that can display the list normally, and when you click Next, the number of pages changes, but the page content is the first page that appears. The system prompts for rows 72nd and 79 undefined variable undefined variable:php_self How do I change it?

 /*error_reporting (e_all ^ e_notice); * *
##################### #课题列表 ##########################
Include "config.php";
Include "header.php";
?>

 
  
 


 
  
 
<title>List of topics</title>


































 
  $n = 0;$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 the 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 " 
   
     ";} else{echo " 
   
     "; }if ($row [' Surplus ']==0) $ss = "not selectable"; else $ss = "optional"; Echo 
    
  
  
  
 
   
 
    
 
Project number
 
    
Project name
 
    
Teacher Guidance
 
    
Title
 
    
Optional number
 
    
Selection of topics
 
    
State
 
    
Detailed information
 
   
 
   
". $row [' id ']."
 
    
". $row [' Subject ']."