Pl/PgSql: Loop over Array

Ist it possible to loop over an array:

CREATE FUNCTION atest(INT[]) RETURNS TEXT AS '
    DECLARE
        myA ALIAS FOR $1;
        myI INT;
        myRet TEXT='''';
    BEGIN
        FOR myI IN myA LOOP
            myRet=myRet||''x''||myI;
        END LOOP;
        RETURN myRet;
    END;
' LANGUAGE 'plpgsql';

This Examle is not working ;-(

Thanks,
AXEL.