// Prepare checkbox value which will be used in SQL statement.
  // In this function, we add all the numbers in $$checkboxlist parameter.
  // If checkboxlist is empty, then we return 0.
  //
  // Arguments:
  // checkboxlist ; the value of CHECKBOXLIST parameter in the GetPOI request.
  //
  // Returns:
  // checkbox_value ; the value that can be used to construct the right
  // SQL statement.
  
  function GetCheckboxValue ( $$checkboxlist ) {
          // if checkboxlist exists, prepare checkbox_value.
          if( isset( $$checkboxlist ) ) {
          // Initialize returned value to be 0 if checkboxlist is empty.
          $$checkbox_value = 0;
          // If checkboxlist is not empty, return the added value of all
          // the numbers splited by ‘,’.
  
          if (!empty($$checkboxlist)) {
                  if ( strstr(checkboxlist,’,’) ) {
                          $$checkbox_array = explode(‘,’, checkboxlist);
                                  for( $$i=0; i<count($$checkbox_array); i++ )
                          $$checkbox_value+=checkbox_array[$$i];
                  }//if
          else
                  checkbox_value = $$checkboxlist;
          }//if
          return checkbox_value;
          } //if
          else {
          throw new Exception(“checkboxlist parameter is not passed in GetPOI request.”);
          }//else
  }//GetCheckboxValueCustom Slider Filter