Plugin Resolution [Flatpress]

<?php
/*
Plugin Name: Resolution
Plugin URI: http://www.pierovdfn.it/
Description: Adds a custom stylesheet for every resolution
Author: Piero VDFN
Version: 1.0
Author URI: http://www.pierovdfn.it/
*/

/*
 * HOW TO CONFIGURE THE PLUGIN
 *
 * To configure the stylesheets please go to line 69 and modify the array
 * of the function "getStylesheets" with the resolution as key and the
 * complete URL as value.
 *
 * You can get the URL of the theme by using the function
 * theme_geturl('yourthemename') or
 * theme_style_geturl('yourstyle', 'yourtheme').
 */

class PluginResolution {

    /**
     * The custom stylesheet to add to the header.
     *
     * @var string
     * @access private
     */
    private $stylesheet = '';

    /**
     * The name of the cookie that stores the resolution.
     *
     * @var string
     * @access private
     */
    private $cookieName = 'pl_resolution';

    /**
     * The duration of the cookie that stores the resolution in seconds.
     *
     * @var integer
     * @access private
     */
    private $cookieDuration = 2678400; // 31 days

    /**
     * The constructor of the class. Registers hooks.
     */
    public function __construct()
    {
        add_action('init', array($this, 'init'));
        add_action('wp_head', array($this, 'head'));
    }

    /**
     * Return the array of stylesheets.
     *
     * This is done using a function instead of a member so the user can
     * call other functions.
     *
     * The function must return an array with resolutions as keys and URLs
     * as values. URLs must be complete URL.
     *
     * @return array: see the description
     */
    private function getStylesheets()
    {
        $styles = array(
            //'yourresoltion' => theme_style_geturl('yourtheme', 'yourstyle') . 'file.css',
            '1280x1024' => theme_style_geturl('yourstyle', 'yourtheme') . 'file.css',
        );

        return $styles;
    }

    /**
     * Handles the init hook.
     */
    public function init()
    {
        $res = @$_COOKIE[$this->cookieName];
        if(isset($_GET['resolution'])) {
            $res = $_GET['resolution'];
        }

        $styles = $this->getStylesheets();
        if(!empty($res) && isset($styles[$res])) {
            setcookie($this->cookieName, $res, time() + $this->cookieDuration, BLOG_ROOT);
            $this->stylesheet = $styles[$res];
        } elseif(!empty($_COOKIE[$this->cookieName])) {
            setcookie($this->cookieName, '', time() - 1000, BLOG_ROOT);
        }
    }

    /**
     * Handles the wp_head hook.
     */
    public function head()
    {
        if(!empty($this->stylesheet)) {
            echo "\n" . '<link rel="stylesheet" href="' . $this->stylesheet . '" type="text/css" />' . "\n";
        }
    }
}

new PluginResolution();