public Iterator entriesIterator() {
        return new EntriesIterator(this);
    }
Gets an iterator over the map.
Changes made to the iterator affect this map.
<p/>
A MapIterator returns the keys in the map. It also provides convenient
methods to get the key and value, and set the value.
It avoids the need to create an entrySet/keySet/values object.
It also avoids creating the Map.Entry object.

@return the map iterator
jphp-runtime/src/php/runtime/memory/support/ArrayMemoryMap.java