--TEST-- MongoDB\BSON\Undefined::jsonSerialize() with json_encode() --FILE-- <?php require_once __DIR__ . '/../utils/tools.php'; $doc = MongoDB\BSON\toPHP(MongoDB\BSON\fromJSON('{ "foo": {"$undefined": true} }')); $json = json_encode($doc); echo toJSON(fromPHP($doc)), "\n"; echo $json, "\n"; var_dump(toPHP(fromJSON($json))); ?> ===DONE=== <?php exit(0); ?> --EXPECTF-- { "foo" : { "$undefined" : true } } {"foo":{"$undefined":true}} object(stdClass)#%d (%d) { ["foo"]=> object(MongoDB\BSON\Undefined)#%d (%d) { } } ===DONE===