I have an object with a single key and its value. But I don\'t know the key to access it. What is the most efficient way to get the key without enumerating the object?
If you just want to access the value, you don't need the key (actually property name) at all:
$value = current((array)$object);
If you really want the property name, try this:
$key = key((array)$object);