XML : How to use XMLElement() to get this oracle table outputs

I am new in pl/sql and xml. I want fetch data as xml format from a table by calling user define function:

This the table sql:

  CREATE TABLE "HIMADRI"."PAYROLLFILE"      (    "SALYR" NUMBER(4,0) NOT NULL ENABLE,       "SALMT" NUMBER(2,0) NOT NULL ENABLE,       "EMPID" NUMBER NOT NULL ENABLE,       "DPTID" NUMBER NOT NULL ENABLE,       "SALHD" VARCHAR2(2 BYTE) NOT NULL ENABLE,       "DESCR" VARCHAR2(50 BYTE) NOT NULL ENABLE,       "ALAMT" FLOAT(126) NOT NULL ENABLE,       "OPID" NUMBER NOT NULL ENABLE,       "TRADT" DATE);    

I want to get data in following xml format:

    <transaction>              <salary_year>SALYR</salary_year>              <salary_month>SALMT</salary_month>              <employee_id>EMPID</employee_id>              <department_code>DPTID</department_code>              <salary_head>SALHD</salary_head>              <description>DESCR</description>              <amount>ALAMT</amount>              <operator_id>OPID</operator_id>              <transaction_date>TRADT</transaction_date>  </transaction>    

How should i write pl/sql function body:

  FUNCTION get_all_payroll_transactions RETURN  VARCHAR2 IS  isSuccess VARCHAR2(50);       BEGIN          END get_all_payroll_transactions;    

How should i call the function from php:

  $stid = oci_parse($conn, " begin                                    :result :=  PAYROLL.get_all_payroll_transactions();                                                          end;" );            oci_bind_by_name($stid, ':result',$ru, 500);          oci_execute($stid);    

please give me clue.Thanks