wordpress-skeleton/blog/wp-content/plugins/w3-total-cache/lib/W3/Plugin.php

<?php

/**
 * W3 Plugin base class
 */

/**
 * Class W3_Plugin
 */
class W3_Plugin
{
    /**
     * Config
     *
     * @var W3_Config
     */
    var $_config = null;
    
    /**
     * PHP5 Constructor
     */
    function __construct()
    {
        require_once W3TC_LIB_W3_DIR . '/Config.php';
        
        $this->_config = & W3_Config::instance();
    }
    
    /**
     * PHP4 Constructor
     *
     * @return W3_Plugin
     */
    function W3_Plugin()
    {
        $this->__construct();
    }
    
    /**
     * Runs plugin
     */
    function run()
    {
    }
    
    /**
     * Returns plugin instance
     *
     * @return W3_Plugin
     */
    function &instance()
    {
        static $instances = array();
        
        if (! isset($instances[0])) {
            $class = __CLASS__;
            $instances[0] = & new $class();
        }
        
        return $instances[0];
    }
    
    /**
     * Check if plugin is locked
     *
     * @return boolean
     */
    function locked()
    {
        static $locked = null;
        
        if ($locked === null) {
            if (w3_is_wpmu()) {
                if (isset($_GET['sitewide'])) {
                    $locked = false;
                } else {
                    global $blog_id;
                    
                    $blogs = get_blog_list();
                    
                    foreach ($blogs as $blog) {
                        if ($blog['blog_id'] != $blog_id) {
                            $active_plugins = get_blog_option($blog['blog_id'], 'active_plugins');
                            
                            if (in_array(W3TC_FILE, $active_plugins)) {
                                $locked = true;
                                break;
                            }
                        }
                    }
                }
            } else {
                $locked = false;
            }
        }
        
        return $locked;
    }
}