Session Variable Help

I'm building a page/form that will allow users to add new rows to my database.  I want to auto-populate the 'student_id' column in the table they are inserting into with the information contained in my table 'users' that contains their login information.  In both tables, their numeric id is 'student_id'. I have their username = their email.

How is this done?

to recap, i have them inserting rows into a table called sponsors.  I want the column sponsors.student_id to autopopulate with their student_id from the users table based on the fact that they are logged in as said user.

I know this must involve the session variable.. but just have no idea how to write or integrate the syntax…

Thanks in advance for any help!

right now... the insert code from my form looks like the following:

if ((isset($_POST["MM_insert"])) && ($_POST["MM_insert"] == "form3")) {

  $insertSQL = sprintf("INSERT INTO sponsors (studentid, schoolid, sponsorname, sponsor_address1, sponsor_address2, sponsor_city, sponsor_state, sponsor_zip, status, `level`, signed_contract, total_due, pymt_rcvd, prize_rcvd, prize_to_sgf) VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s)",

GetSQLValueString($_POST['studentid'], "int"),

GetSQLValueString($_POST['schoolid'], "int"),

GetSQLValueString($_POST['sponsorname'], "text"),

GetSQLValueString($_POST['sponsor_address1'], "text"),

GetSQLValueString($_POST['sponsor_address2'], "text"),

GetSQLValueString($_POST['sponsor_city'], "text"),

GetSQLValueString($_POST['sponsor_state'], "text"),

GetSQLValueString($_POST['sponsor_zip'], "int"),

GetSQLValueString($_POST['status'], "text"),

GetSQLValueString($_POST['level'], "text"),

GetSQLValueString($_POST['signed_contract'], "date"),

GetSQLValueString($_POST['total_due'], "double"),

GetSQLValueString($_POST['pymt_rcvd'], "date"),

GetSQLValueString($_POST['prize_rcvd'], "date"),

GetSQLValueString($_POST['prize_to_sgf'], "date"));

I have studentid and schoolid hidden so students can't populate them... i want them populated by the session variable..   right now my session variable for this page looks like this:

if (!isset($_SESSION)) {

  session_start();

}

$MM_authorizedUsers = "";

$MM_donotCheckaccess = "true";

// *** Restrict Access To Page: Grant or deny access to this page

function isAuthorized($strUsers, $strGroups, $UserName, $UserGroup) {

  // For security, start by assuming the visitor is NOT authorized.

  $isValid = False;

  // When a visitor has logged into this site, the Session variable MM_Username set equal to their username.

  // Therefore, we know that a user is NOT logged in if that Session variable is blank.

  if (!empty($UserName)) {

    // Besides being logged in, you may restrict access to only certain users based on an ID established when they login.

    // Parse the strings into arrays.

    $arrUsers = Explode(",", $strUsers);

    $arrGroups = Explode(",", $strGroups);

    if (in_array($UserName, $arrUsers)) {

      $isValid = true;

    }

    // Or, you may restrict access to only certain users based on their username.

    if (in_array($UserGroup, $arrGroups)) {

      $isValid = true;

    }

    if (($strUsers == "") && true) {

      $isValid = true;

    }

  }

  return $isValid;

}

$MM_restrictGoTo = "index.php";

if (!((isset($_SESSION['MM_Username'])) && (isAuthorized("",$MM_authorizedUsers, $_SESSION['MM_Username'], $_SESSION['MM_UserGroup'])))) { 

  $MM_qsChar = "?";

  $MM_referrer = $_SERVER['PHP_SELF'];

  if (strpos($MM_restrictGoTo, "?")) $MM_qsChar = "&";

  if (isset($_SERVER['QUERY_STRING']) && strlen($_SERVER['QUERY_STRING']) > 0)

  $MM_referrer .= "?" . $_SERVER['QUERY_STRING'];

  $MM_restrictGoTo = $MM_restrictGoTo. $MM_qsChar . "accesscheck=" . urlencode($MM_referrer);

  header("Location: ". $MM_restrictGoTo);

  exit;

}

?>

given all of this information... are you able to help me with inserting the correct information/syntax here so that i can capture from my users table the studentid and schoolid to be inserted into the sponsors table?