why it will add a blank after the output value

[admin]

$stmt=OCIParse($conn,"BEGIN pkg_test.dbp_sale_test('999',$bb_no,:freq,:addr_num);END;");

the procedure like this:

PROCEDURE dbp_sale_test
(i_radio in char,
i_bb_no in number,
freq1 in out char,
addr_num out char)


if I set freq="001" in my program ,
but in the procedure the freq will set "001 "
it will add the blank after it.

why?