mixed *slice_array(mixed *arr,int from,int to)

Returns an array that is a slice of the array 'arr' from the index 'from' to
the index 'to'. Indexes are numbered 0-

If 'arr' is not an array or indexes are outside the limits of 'arr', 
then 0 will be returned.

Note also that you can use the operator '+' on arrays.

