This is quite dumb, but if you really want to have the named variable exported to the global namespace, you can use
extract()e.g.
$data = '{"success":true,"name":"winspiral","total":196864,"withdrawn":0,"balance":196864}';
extract((array)json_decode($data), EXTR_SKIP);
echo "Hey $name, your balance is $balance";
Anyway, you shouldn't do this and avoid trashing the global namespace (or current scope), just use a regular object, like :
$obj = json_decode($data);
echo "Hey $obj->name, your balance is $obj->balance";