How to download multiple images from server database?

public class GalleryFragment extends Fragment {
	
	ProgressBar progressBar;
	TextView progressText;
	
	 JSONParser jsonParser = new JSONParser();
	    
	 private static String url_download_photo_id = Global.url+"/clubs/download_photo_id.php";
	 private static String url_download_photo = Global.url+"/clubs/download_photo.php";
	 
	 private static final String TAG_SUCCESS = "success";
	 private static final String TAG_CLUBS = "clubs";
	 private static final String TAG_PHOTO = "photo";
	 private static final String TAG_PHOTO_ID = "photo_id";
	 
	 // News JSONArray
	JSONArray clubs = null;
	
	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {

		View rootView = inflater.inflate(R.layout.fragment_gallery, container, false);
		
        progressText = (TextView) rootView.findViewById(R.id.textView1);

	    //Progress Bar
		progressBar = (ProgressBar) rootView.findViewById( R.id.progressBar1); 
		
		new DownloadPhotoId().execute();
	
	return rootView;
	}
	
    class DownloadPhotoId extends AsyncTask<string,> {
		
        protected String doInBackground(String... args) {
        	
        	Log.v("DownloadPhotoId","doInBackground");
  
            // check for success tag
            try {
            	
                // Building Parameters
                List<namevaluepair> params = new ArrayList<namevaluepair>();
                params.add(new BasicNameValuePair("club_id", ClubActivity.club_id));
     
                JSONObject json = jsonParser.makeHttpRequest(url_download_photo_id,"GET", params);
     
                // check log cat for response
                Log.d("Download Image Id", json.toString());
                
                int success = json.getInt(TAG_SUCCESS);
 
                if (success == 1) {       
                	
               	 getActivity().runOnUiThread(new Runnable() {
          		    public void run() {
          		       progressBar.setVisibility(View.VISIBLE);
          		    }
          		});
                	
                	clubs = json.getJSONArray(TAG_CLUBS);
               	 
               	 	progressBar.setMax(clubs.length());

                    for (int i = 0; i < clubs.length(); i++) {
                   	 JSONObject c = clubs.getJSONObject(i);
                 
                        // Storing each json item in variable
                        String photo_id = c.getString(TAG_PHOTO_ID);
                   
            			progressBar.setProgress(i+1);
            			
            			Log.v("Photo id"+i,""+photo_id);
            			
            			new DownloadPhoto(photo_id).execute();
                    }
                    
                    getActivity().runOnUiThread(new Runnable() {
              		    public void run() {
              		    	 progressBar.setVisibility(View.INVISIBLE);
              		    }
              		});
                }
                else 
                {
                	
                }
            
            } catch (JSONException e) {
            	problem();
                e.printStackTrace();             
            }
            catch(Exception e)
            {
            	problem();
            	Log.v("Exception",""+e);           	
            }
       
            return null;
        }
 
        protected void onPostExecute(String file_url) {

        }
    }
    
class DownloadPhoto extends AsyncTask<string,> {
	
	String photo_id = null;
	DownloadPhoto(String pId)
	{
		photo_id = pId;
	}
		
        protected String doInBackground(String... args) {
        	
        	Log.v("DownloadPhoto","doInBackground");
  
            // check for success tag
            try {
            	
                // Building Parameters
                List<namevaluepair> params = new ArrayList<namevaluepair>();
                params.add(new BasicNameValuePair("photo_id", photo_id));
     
                JSONObject json = jsonParser.makeHttpRequest(url_download_photo,"GET", params);
     
                // check log cat for response
                Log.d("Download Image Id", json.toString());
                
                int success = json.getInt(TAG_SUCCESS);
 
                if (success == 1) {       
                	
                	clubs = json.getJSONArray(TAG_CLUBS);

                   	 JSONObject c = clubs.getJSONObject(0);
                 
                        // Storing each json item in variable
                        String photo = c.getString(TAG_PHOTO);

            			Log.v("Photo id "+photo_id,""+photo);
                }
                else 
                {
                	
                }
            
            } catch (JSONException e) {
            	problem();
                e.printStackTrace();             
            }
            catch(Exception e)
            {
            	problem();
            	Log.v("Exception",""+e);           	
            }
       
            return null;
        }
 
        protected void onPostExecute(String file_url) {

        }
    }

	void problem()
	{
		getActivity().runOnUiThread(new Runnable() {
		    public void run() {
		    	 Toast.makeText(getActivity(), "Something went wrong! Try again!",Toast.LENGTH_LONG).show();
		    	progressBar.setVisibility(View.INVISIBLE);
				progressText.setVisibility(View.INVISIBLE);
			    }
			});
	}
}

$response = array();
 
// include db connect class
require_once __DIR__ . '/db_connect.php';
 
// connecting to db
$db = new DB_CONNECT();

// check for post data
if (isset($_GET["club_id"])) {
    $club_id = $_GET['club_id'];

	$result = mysql_query("SELECT photo_id FROM gallery WHERE club_id = '$club_id'") or die(mysql_error());
 
	if (!empty($result)) {
		// check for empty result
		if (mysql_num_rows($result) > 0) {

			$response["clubs"] = array();
 
			while ($row = mysql_fetch_array($result)) {

				$clubs = array();
				$clubs["photo_id"] = $row["photo_id"];
				
				array_push($response["clubs"], $clubs);
			}
			// success
			$response["success"] = 1;
 
			// echoing JSON response
			echo json_encode($response);
		}
		else {
			$response["success"] = 0;
			$response["message"] = "Not found";
 
			// echo no users JSON
			echo json_encode($response);
		}
	}
	else {
		$response["success"] = 0;
		$response["message"] = "Not found";
 
		// echo no clubs JSON
		echo json_encode($response);
	}
}
else {
    // required field is missing
    $response["success"] = 0;
    $response["message"] = "Required field(s) is missing";
 
    // echoing clubs response
    echo json_encode($response);
}
?>

$response = array();
 
// include db connect class
require_once __DIR__ . '/db_connect.php';
 
// connecting to db
$db = new DB_CONNECT();

// check for post data
if (isset($_GET["photo_id"])) {
    $photo_id = $_GET['photo_id'];

	$result = mysql_query("SELECT photo FROM gallery WHERE photo_id = '$photo_id'") or die(mysql_error());
 
	if (!empty($result)) {
		// check for empty result
		if (mysql_num_rows($result) > 0) {
			$response["clubs"] = array();
 
			while ($row = mysql_fetch_array($result)) {
				$clubs = array();
				$clubs["photo"] = $row["photo"];
				
				array_push($response["clubs"], $clubs);
			}
			// success
			$response["success"] = 1;
 
			// echoing JSON response
			echo json_encode($response);
		}
		else {
			$response["success"] = 0;
			$response["message"] = "Not found";
 
			// echo no users JSON
			echo json_encode($response);
		}
	}
	else {
		$response["success"] = 0;
		$response["message"] = "Not found";
 
		// echo no clubs JSON
		echo json_encode($response);
	}
}
else {
    // required field is missing
    $response["success"] = 0;
    $response["message"] = "Required field(s) is missing";
 
    // echoing clubs response
    echo json_encode($response);
}
?>