Cursor did not return data if using variables in the where clause

Question

ENV: report builder 9.0.4.3.0, DB 10g, OS XP
table and data ctvctyp:
ctvctyp_code    ctvctyp_code_pred
   CO               Z1
   FE                   Z1
FUNCTION get_case_type(case_type VARCHAR2) RETURN VARCHAR2 IS
  cursor  type_cur is
    select ctvctyp_code
    from ctvctyp
    where ctvctyp_code_pred = :P_case_type; -- if use 'Z1', it will return 'CO','FE'
                                            -- but if 'Z1' is passed in as case_type, it returns null.
  temp_type     VARCHAR2(4);
  return_type   VARCHAR2(200);
  counter       NUMBER;
BEGIN
     return_type := '';
     counter := 0;
     srw.message(20,'in case_type is '||case_type);
     open type_cur;
     LOOP
          FETCH type_cur INTO temp_type;
          EXIT WHEN type_cur%NOTFOUND;
          counter := counter+1;
          if temp_type is NULL then
               srw.message(20,'temp type is null');
          else
            srw.message(20,temp_type);
          end if;
          if counter = 1 then
               return_type := ''''||temp_type||'''';
          else
               return_type := return_type||','''||temp_type||'''';
          end if;     
     END LOOP;
     return return_type;
END;
In my p_casetype validation trigger:
function P_CaseTypeValidTrigger return boolean is
     tempCaseType   VARCHAR2(200);
     return_type    VARCHAR2(200);
begin
    :P_CASETYPE := 'Z1'
    return_type := get_case_type;   --- I got null returned.
  return (TRUE);
end;
But in sqlplus:
declare a bind variable :P_casetype := 'Z1';
select get_case_type from dual;
returns:   'FE','MI'

Answer 1

cursor type_cur is
select ctvctyp_code
from ctvctyp
where ctvctyp_code_pred = _{color:#0000ff}*:P_case_type;*_{color}Shouldn't be this :p_casetype instead of :p_case_type?