public function addAttachment ($list_name, $list_item_id, $file_name) {
		// base64 encode file
		$attachment = base64_encode(file_get_contents($file_name));

		// Wrap in CAML
		$CAML = '
		<AddAttachment xmlns="http://schemas.microsoft.com/sharepoint/soap/">
			<listName>' . $list_name . '</listName>
			<listItemID>' . $list_item_id . '</listItemID>
			<fileName>' . $file_name . '</fileName>
			<attachment>' . $attachment . '</attachment>
		</AddAttachment>';

		$xmlvar = new \SoapVar($CAML, XSD_ANYXML);

		// Attempt to run operation
		try {
			$this->soapClient->AddAttachment($xmlvar);
		} catch (\SoapFault $fault) {
			$this->onError($fault);
		}

		// Return true on success
		return true;
	}