static
○　Object::obj();
×　$obj->obj();
○　$this->obj();

public
○　Object::obj();
○　$obj->obj();
○　$this->obj();

protected
×　Object::obj();
○　$obj->obj();
○　$this->obj();

private
×　Object::obj();
×　$obj->obj();
○　$this->obj();

これでおｋ？