Unwrap an array into rows in PostgreSQL

What is the fastest way to unwrap array into rows in PostgreSQL? For instance,

We have:

a-{1,2}{2,3,4}

And we need:

b- 12234

I'm using:

select explode_array(a) as a from a_table;

where explode_array is:

create or replace function explode_array(in_array anyarray) returns setof anyelement as$$    select ($1)[s] from generate_series(1,array_upper($1, 1)) as s;$$

Is there any better way?