Strange warning when trying to extend class

Question

I started getting strange warnings, after extending a class that extends another Event_Feed_Item > My_Feed_Item > SimplePie_Item

- Cannot extend from interface 
 'SimplePie_Item'
- Implementors of methods in 
 'SimplePie_Item'

However on runtime it works fine. Also SimplePie_Item is not an interface, it's a simple Class.. Just need to know if I'm running into trouble, or if i can just ignore this warning

EDIT I'm extending this class
Also this is the skeleton from my classes

class My_Feed_Item extends SimplePie_Item // error is triggered here
{
    protected $_source_id = null;

    public function set_source ($source_id)
    {
    }
    public function get_image ()
    {
    }
    public function get_venue_id ()
    {
    }
    public function get_venue_nm ()
    {
    }
    public function cleanString($str)
    {
    }
}

class Event_Feed_Item extends My_Feed_Item
{
    public function get_event_nm ()
    {

    }
    public function get_event_start_dt ()
    {

    }
    public function get_event_end_dt ()
    {
    }

}

Answer 1

I was having the same issue. Make sure the Build Path and/or Include Path for the project in Zend Studio have the path to the directory where the parent class is located. In PHP Explorer, right-click the project and choose Build Path -> Configure Build Path. Or right-click the project and choose Include Path -> Configure Include Path.