/**
  * Return an instance of this class.
  *
  * @since     1.0.0
  *
  * @return    object    A single instance of this class.
  */
 public static function get_instance()
 {
     // If the single instance hasn't been set, set it now.
     if (null == self::$instance) {
         self::$instance = new self();
     }
     return self::$instance;
 }
<?php

/**
 * @package   Flickr Picturefill
 * @author    Adam Wills <*****@*****.**>
 * @license   MIT/GPLv2
 * @link      http://adamwills.com
 * @copyright 2013 Adam Wills
 *
 * Plugin Name: Flickr Picturefill
 * Plugin URI:  http://adamwills.com/
 * Description: A plugin that combines the power of picturefill and the Flickr API to provide responsive images
 * Version:     2.0.0
 * Author:      Adam Wills
 * Author URI:  http://adamwills.com
 * Text Domain: plugin-name-locale
 * License:     GPL-2.0+
 * License URI: http://www.gnu.org/licenses/gpl-2.0.txt
 * Domain Path: /lang
 */
// If this file is called directly, abort.
if (!defined('WPINC')) {
    die;
}
require_once plugin_dir_path(__FILE__) . 'class-flickr-picturefill.php';
Flickr_Picturefill::get_instance();