PHP datatype vs Oracle Varchar2

Hi, The comparison between Oracle VARCHAR2 and a PHP string doesn't seems to work. Detail as follows: I have one PHP variable and one Oracle column: . $form_user_id: a PHP string obtained from web form input, such as 'user1'. . Username: an oracle table column of type VARCHAR2(20). The following sql statement failed: "select * from mytable where Username='$form_user_id'" It failed because Username has a strlen of 20, where $form_user_id has a strlen of 5. If I changed the Username from VARCHAR2(20) to CHAR(20), then this sql worked fine. But I think with Oracle VARCHAR2, the strlen of Username in this case should be 5 instead of 20. Victoria Zhou