Fatal error: Uncaught Error: Interface "MediaWiki\Json\JsonUnserializable" not found in /var/www/html/extensions/SemanticMediaWiki/includes/dataitems/SMW_DataItem.php:33 Stack trace: #0 {main} thrown in /var/www/html/extensions/SemanticMediaWiki/includes/dataitems/SMW_DataItem.php on line 33