Pear DB problem with autoExecute

Hello, sorry for the following long code!! i work with a simple-class to handle my db-calls if i work with with all others methods in this class then works fin but if i work with autoexecute comes an error this error is at bottom on the message! No my class require_once("DB.php"); class base_db_ebay { var $dbcon; var $lasterror; var $printerrors =TRUE;

          function base_db_ebay()
          {
              $this->connect();
          }

         function connect()
         {
              if(!($this->isConnected()))
              {
                   $this->dbcon = & DB::connect(DB_DSN, true)

. . . usw.

             function isConnected()
             {
                  if(is_object($this->dbcon) && is_subclass_of($this->dbcon,"db_common"))
                       return TRUE;
                  return FALSE;
             }

//the update works fine

             function update($updatestr, $updatearr)
             {
              $result = FALSE;
              if($this->connect())
              {
                   $res = $this->dbcon->prepare($updatestr);
                    $res = $this->dbcon->execute($res,$updatearr);
                       if(DB::isError($res))
                       {
                            $this->setLastError($res);
                       }
                        elseif($res === DB_OK)
                        {
                            $result = $this->dbcon->affectedRows();
                        }
              return $result;
             }

// und now my problem-section

       function autoinsert($tableName,$tableFields,$querytype)
          if($this->connect())
              {
                      $result =$this->$dbcon->autoExecute($tableName,$tableFields, $querytype);
                    if (DB::isError($result)) {
                        die($sth->getMessage());
                    }
                }
        }

} if i call autoinsert with $DB_con = &new base_db_ebay(); $DB_con->autoinsert($tableName="mytable",$arrOrder,'DB_AUTOQUERY_INSERT' ); then comes Call to a member function autoExecute() on a non-object in i couldn't understood this if i call all other methos then works fine if i call autoexecute from an other script directly like $table_name = 'user'; $table_fields = array('id', 'name', 'country'); $sth = $db->autoPrepare($table_name, $table_fields,

                        DB_AUTOQUERY_INSERT);

works also fine could any help best regards Achim