@Override public V get(Object key) {
        if (!(key instanceof String)) {
            return super.get(key);
        }
        return super.get(convertKey((String) key));
    }
Converts keys to lower case.
<p/>
Returns null if key is null.

@param key the key convert
@return the converted key
jphp-runtime/src/php/runtime/common/collections/map/CaseInsensitiveMap.java