如何在Wordpress中覆盖插件类的功能？

I want to override function get_post() in class EM_Tickets of plugin Event Manager

class EM_Tickets extends EM_Object implements Iterator{
/**
 * Retrieve multiple ticket info via POST
 * @return boolean
 */
function get_post(){
    // something here

    return apply_filters('em_tickets_get_post', count($this->errors) == 0, $this);
    }
}

so I create my own plugin and put below codes but no luck, don't know why it's not working although I read and follow some manuals likes Is it possible to replace a function within a PHP class?

class EM_Tickets_Child extends EM_Tickets implements Iterator{

    public function get_post(){
        file_put_contents('log.txt', 'in child class', FILE_APPEND | LOCK_EX);
        //something here
    }           
}

You have a filter (apply_filters) on the original code. You just need to hook and create a function to override the returns value, no needs to extends the plugin class, but it's another way to do.

add_action('em_ticket_get_posts', array('Em_tickets', 'my_new_get_post), 10, 2);