Description:
------------
Fatal error: Call to a member function bind_param() on a non-object in C:\wamp\www\deftmd\classes\DAL\AppointDAO.php on line 151

iam getting almost all file this erroe 

Reproduce code:
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public function insert(&$conn, Appoint &$appt) {
       
  	
   $start_time = strtotime($appt->appt_start_ts);

   Debug::createInstance()->println("Inside AppointDAO Insert " . $appt->starthour );

   $start_time = $start_time + $appt->starthour * 60 * 60;
   $end_time = $start_time + $appt->duration * 60;
   $appt->appt_start_ts = date('Y-m-d H:i:s', $start_time);
   $appt->appt_end_ts = date('Y-m-d H:i:s', $end_time);

   Debug::createInstance()->println("Inside AppointDAO Insert ". $appt->appt_start_ts);
   Debug::createInstance()->println("Inside AppointDAO Insert ". $appt->appt_end_ts);

   

   try {

        Debug::createInstance()->println("Inside AppointDAO Insert Provider ");

        Debug::createInstance()->println("Inside AppointDAO Insert Provider ". $appt->duration);

        Debug::createInstance()->println("Inside AppointDAO Insert Provider ". $appt->provider->id);        

	   $InsertSQL = "INSERT INTO APPOINTMENTS(APPT_TYPE, EVENT, EVENT_DESC, APPT_START_TS, DURATION, APPT_END_TS, PROVIDER_ID, LOCATION_ID) VALUES(?,?,?,?,?,?,?,?)";

        $stmt = $conn->prepare($InsertSQL);

        $stmt->bind_param("ssssisii", 
                             $appt->appt_type,
			     $appt->event,
			     $appt->event_desc,
			     $appt->appt_start_ts,
			     $appt->duration, 
			     $appt->appt_end_ts,
			     $appt->provider->id,
                             $appt->location_id
                         );
      
        $stmt->execute();
        $appt->id = $stmt->insert_id;

        Debug::createInstance()->println("Inside AppointDAO Generated ID ". $appt->id);        
        
        if ($appt->patient->id != null) {
        $UpdateSQL = "UPDATE APPOINTMENTS SET PATIENT_ID=? WHERE ID=? ";
        $stmt = $conn->prepare($UpdateSQL);
        Debug::createInstance()->println("Inside AppointDAO Update ");        
        $stmt->bind_param("ii", $appt->patient->id, $appt->id);
        $stmt->execute();
        Debug::createInstance()->println("Inside AppointDAO Update Executed ");        
        }
    
    
    
    $stmt->close();
   }
    catch(Exception $e) {
   $stmt->close();
   throw new SQLException("Unable to insert record into Appointments Table");
   
   } 

  }

Expected result:
----------------
create a record