如何在导入Excel文件时重复输入更新 - php mysql

this is code I want to import sql with php I tried but failed, someone could help

     $target = basename($_FILES['nilaip']['name']) ;
            move_uploaded_file($_FILES['nilaip']['tmp_name'], $target);        
            $data = new Spreadsheet_Excel_Reader($_FILES['nilaip']['name'],false);        
            $baris = $data->rowcount($sheet_index=0);       
              $drop = isset( $_POST["drop"] ) ? $_POST["drop"] : 0 ;
            if($drop == 1){     
                 $truncate ="TRUNCATE TABLE rb_nilai_pengetahuan_semester";
                 mysql_query($truncate);
            };   
              for ($i=2; $i<=$baris; $i++){      
              $nisn         = $data->val($i, 2);
              $nilai1       = $data->val($i, 4);
              $nilai2       = $data->val($i, 5);                    
$cek = "SELECT id_nilai_pengetahuan_semester WHERE id_nilai_pengetahuan_semester ='".$id_nilai_pengetahuan_semester."'";
              $que = db_query($cek);
              $pfetch = dba_fetch($que);
              if($id_nilai_pengetahuan_semester == $pfetch['id_nilai_pengetahuan_semester']){ 
?>