public int hashCode() {
        return (getKey() == null ? 0 : getKey().hashCode()) ^ (getValue() == null ? 0 : getValue().hashCode());
    }
Gets a hashCode compatible with the equals method.
<p/>
Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}

@return a suitable hash code
jphp-runtime/src/php/runtime/common/collections/keyvalue/AbstractMapEntry.java