Ryan McCue有个好主意plugin Hopper: 为自定义筛选器添加回调以返回当前实例。

插件的示例代码：

class Plugin_Class {
    public function __construct()
    {
        add_filter( \'get_plugin_class\', array ( $this, \'provide_instance\' ) );
    }

    function provide_instance() {
        return $this;
    }
}

$plugin_class = apply_filters( \'get_plugin_class\', NULL );

if ( is_a( $plugin_class, \'Plugin_Class\' ) )
{
    // use the plugin class instance
}