Php paging problems system prompts Undefinedvariable: php_self

The system prompts "Undefinedvariable: php_self" for the Undefinedvariable variable in php paging. the page displays the list normally. when you click "next page", the page number changes, however, the page content is displayed on the first page. The system prompts the Undefined variable Undefined & nbsp; variable: & nbsp; php_self & n php paging. the system prompts the Undefined variable: php_self.
This page is a page that can normally display the list. when you click "next page", the page number changes, but the page content is still the first page. The system prompts rows 72nd and 79 Undefined variables: php_self. how can I modify them?

 /* Error_reporting (E_ALL ^ E_NOTICE );*/
############## ############
Include "config. php ";
Include "header. php ";
?>

 
  

  

  
   

   Project List
   

   
    

    
    

    

    
     
 
     

     

      
        Subject No.
       
 
       

       
         Topic Name
        

        
          Instructor
         

         
           Title
          

          
            Number of persons available
           

           
             Selection
            

            
              Status
             

             
               Details
              

              

              $ 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"
              
                ";}
               
Else {
               
Echo"
               
                 ";
                
}
                
If ($ row ['Surplus '] = 0)
                
$ Ss = "not available ";
                
Else $ ss = "optional ";
                
Echo"
                

                
                  ". $ Row ['id']."
                 

                 
                   ". $ Row ['subobject']."