Problems getting data into a SET Column

Question

I am having a problem with the SET Column storing multiple days of the week.  When I submit the form, a link that says function.implode shows up at the top of the page and enters NULL in my Column.  Any ideas why?  I also had a lot of server side validation that was in this code.  I removed all of it thinking that might be the problem, but the same thing is happening either way.
Here is the code:
mysql_select_db($database_connRegister, $connRegister);
$query_getusers = "SELECT * FROM users";
$getusers = mysql_query($query_getusers, $connRegister) or die(mysql_error());
$row_getusers = mysql_fetch_assoc($getusers);
$totalRows_getusers = mysql_num_rows($getusers);
$editFormAction = $_SERVER['PHP_SELF'];
if (isset($_SERVER['QUERY_STRING'])) {
  $editFormAction .= "?" . htmlentities($_SERVER['QUERY_STRING']);
if ((isset($_POST["MM_insert"])) && ($_POST["MM_insert"] == "sign_form")) {
if (isset($_POST['days_to_play'])) {
  $_POST['days_to_play'] = implode(',', $_POST['days_to_play']);
} else {
  $_POST['days_to_play'] = 'Monday';
  $insertSQL = sprintf("INSERT INTO users (user_name, password, first_name, last_name, address, city, `state`, zip, phone_number, member_since, email, days_to_play, handicap, home_course, play_in_tournaments, casual_compet, hear_about_us, confirm_pass, site_city, text) VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s)",
                       GetSQLValueString($_POST['user_name'], "text"),
                       GetSQLValueString($_POST['password2'], "text"),
                       GetSQLValueString($_POST['first_name'], "text"),
                       GetSQLValueString($_POST['last_name'], "text"),
                       GetSQLValueString($_POST['address'], "text"),
                       GetSQLValueString($_POST['city'], "text"),
                       GetSQLValueString($_POST['state'], "text"),
                       GetSQLValueString($_POST['zip'], "int"),
                       GetSQLValueString($_POST['phone_number'], "text"),
                       GetSQLValueString($_POST['member_since'], "defined", 'NOW()'),
                       GetSQLValueString($_POST['email'], "text"),
                       GetSQLValueString($_POST['days_to_play'], "text"),
                       GetSQLValueString($_POST['handicap'], "int"),
                       GetSQLValueString($_POST['home_course'], "text"),
                       GetSQLValueString($_POST['play_in_tournaments'], "text"),
                       GetSQLValueString($_POST['casual_compet'], "text"),
                       GetSQLValueString($_POST['hear_about_us'], "text"),
                       GetSQLValueString($_POST['confirm_pass'], "text"),
                       GetSQLValueString($_POST['site_city'], "text"),
                       GetSQLValueString($_POST['text'], "text"));
  mysql_select_db($database_connRegister, $connRegister);
  $Result1 = mysql_query($insertSQL, $connRegister) or die(mysql_error());
  $insertGoTo = "golferstats.php";
  if (isset($_SERVER['QUERY_STRING'])) {
    $insertGoTo .= (strpos($insertGoTo, '?')) ? "&" : "?";
    $insertGoTo .= $_SERVER['QUERY_STRING'];
  header(sprintf("Location: %s", $insertGoTo));

Answer 1

Yes, I had actually already caught my mistake before you sent this.  It is
working now.  I have 2 more unrelated questions that can't seem to find in
your book.
#1 - I have an updated page separate from the user input page and I want it
to populate the days_to_play record when they open update so they can edit
these days if they want.  I can't get it to show what is already selected.
#2 - I have quotes that appear on the page and it works fine and selects
them randomly when the page is accessed, but I want to add a picture(s).
How can I add pictures to a database table and get them to display randomly
with the text I already have?
Thanks for your help.  I am enjoying the book!