Step 14 – cmi.core._children

When (if) the course issues the LMSGetValue(‘cmi.core._children’) call, it expects to see a value returned from the LMS. But what is that value?

The SCORM standard says that the cmi.core._children data element should store a list of the other data elements in the cmi.core.* set that are supported by the LMS. Since I’m planning to support the mandatory variables – and only the mandatory elements – that’s simply:

"student_id,student_name,lesson_location,credit,lesson_status,entry,score,total_time,exit,session_time"

The specification also says that this is a read-only data element so the course can’t set it and I don’t have to worry about it changing as we run the course. So I can incorporate this in my code by modifying the getValue.php code like this.

<?php 

/*

VS SCORM - getValue.php 
Rev 2.0 - Sunday, July 05, 2009
Copyright (C) 2009, Addison Robson LLC

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, 
Boston, MA  02110-1301, USA.

*/

//  database login information
require "config.php";

// connect to the database
$link = mysql_connect($dbhost,$dbuser,$dbpass);
mysql_select_db($dbname,$link);

// read GET variable
$varname = trim($_REQUEST['varname']);

// determine value to be returned
switch ($varname) {

  // no variable name supplied
  case "":
    $varvalue = "";
    break;

  // cmi.core._children is always the same
  case "cmi.core._children":
    $varvalue = "student_id,student_name,lesson_location,credit,lesson_status,entry,score,total_time,exit,session_time";
    break;

  // all other variable names
  default:

    // make safe for database
    $safevarname = mysql_escape_string($varname);
    $varvalue = "";

    // read data from the 'scormvars' table
    $result = mysql_query("select varValue from scormvars where (varName='$safevarname')",$link);
    list($varvalue) = mysql_fetch_row($result);

}

// return variable value to the calling program
print $varvalue;

?>

That was easy. Now onto some slightly more complicated elements.