$this->links['_self'] only exists at the top level to describe the current resource. It does not exist within embedded resources. There's a Link type check when _getEmbRes calls getXml which then calls setXMLAttributes and tries to call $this->getSelf() which will not return anything in this case. A null is not of the same type as Link.
$this->links['_self'] only exists at the top level to describe the current resource. It does not exist within embedded resources. There's a Link type check when _getEmbRes calls getXml which then calls setXMLAttributes and tries to call $this->getSelf() which will not return anything in this case. A null is not of the same type as Link.