Pchp.Library.Arrays.key C# (CSharp) Method

        public static PhpValue key(IPhpEnumerable array)
        {
            if (array == null)
            {
                //PhpException.ReferenceNull("array");
                //return null;
                throw new ArgumentNullException();
            }

            if (array.IntrinsicEnumerator.AtEnd)
                return PhpValue.Null;

            // note, key can't be of type PhpReference, hence no dereferencing follows:
            return array.IntrinsicEnumerator.CurrentKey.GetValue();
        }