/// <summary>
/// Removes the first item of an array and reindex integer keys starting from zero.
/// </summary>
/// <param name="array">The array to be shifted.</param>
/// <returns>The removed object.</returns>
/// <remarks>Resets intrinsic enumerator.</remarks>
public static PhpValue array_shift(PhpArray array)
{
if (array == null)
{
//PhpException.ReferenceNull("array");
//return null;
throw new ArgumentNullException();
}
if (array.Count == 0) return PhpValue.Null;
// dereferences result since the array doesn't do so:
var result = array.RemoveFirst().Value; // TODO: PhpVariable.Dereference
// reindexes integer keys starting from zero:
array.ReindexIntegers(0);
array.RestartIntrinsicEnumerator();
return result;
}