protected function getPostTypeIdentifiers($postTypes)
	{
		$postTypeIdentifiers = [];

		foreach($postTypes as $postTypeKey => $value){

			$postTypeModel = $this->getPostType($value);
			if($postTypeModel){

				// Add the real identifier to the array
				array_push($postTypeIdentifiers, $postTypeModel->identifier);
			}
		}

		return $postTypeIdentifiers;
	}