How to count elements in an array?

How can I obtain a count (number) of elements in a text array? Thanks.

test=# \d array                             Table "array" Attribute   |  Type   |                    Modifier
--------------+---------+------------------------------------------------id           | integer | not null default
nextval('array_id_seq'::text)to_group_ids| text[]  |
 
Index: array_pkey

test=#

--- EXAMPLE SELECT ---

test=# select to_group_ids[1] from array where id=1;to_group_ids
--------------1
(1 row)

test=#