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=#