oracle apex rest api

CREATE OR REPLACE FUNCTION add_numbers (p_int_1  IN  NUMBER,
                                        p_int_2  IN  NUMBER)
  RETURN NUMBER
AS
  l_clob    CLOB;
  l_result  VARCHAR2(32767);
BEGIN

  -- Get the XML response from the web service.
  l_clob := APEX_WEB_SERVICE.make_rest_request(
    p_url         => 'http://oracle-base.com/webservices/add-numbers.php',
    p_http_method => 'GET',
    p_parm_name   => APEX_UTIL.string_to_table('p_int_1:p_int_2'),
    p_parm_value  => APEX_UTIL.string_to_table(p_int_1 || ':' || p_int_2)
  );

  -- Display the whole document returned.
  DBMS_OUTPUT.put_line('l_clob=' || l_clob);

  -- Pull out the specific value of interest.
  l_result := APEX_WEB_SERVICE.parse_xml(
    p_xml   => XMLTYPE(l_clob),
    p_xpath => '//answer/number/text()'
  );

  DBMS_OUTPUT.put_line('l_result=' || l_result);

  RETURN TO_NUMBER(l_result);
END;
/