dynamic list box multiple select - option selected problem

I've really gone to town here:

here is your database SQL:
-----------------------
CREATE TABLE `artist_style` (
  `artist_id` int(11) NOT NULL default '0',
  `style_id` int(11) NOT NULL default '0',
  KEY `artist_id` (`artist_id`)
) TYPE=MyISAM;

INSERT INTO `artist_style` VALUES (2, 1);
INSERT INTO `artist_style` VALUES (1, 3);

CREATE TABLE `artists` (
  `artist_id` int(11) NOT NULL auto_increment,
  `name` varchar(40) NOT NULL default '',
  PRIMARY KEY  (`artist_id`)
) TYPE=MyISAM AUTO_INCREMENT=6 ;

INSERT INTO `artists` VALUES (1, 'skatellites');
INSERT INTO `artists` VALUES (2, 'lead zep');

CREATE TABLE `styles` (
  `style_id` int(11) NOT NULL auto_increment,
  `name` varchar(40) NOT NULL default '',
  PRIMARY KEY  (`style_id`)
) TYPE=MyISAM AUTO_INCREMENT=4 ;

INSERT INTO `styles` VALUES (1, 'rock & roll');
INSERT INTO `styles` VALUES (2, 'folk');
INSERT INTO `styles` VALUES (3, 'ska');
---------------------

Here is a PHP page which does the whole thing:
-----------------------
<?php

$DB=mysql_connect("localhost","test","test");
mysql_select_db("test");

if(isset($_POST['save'])){
      $id=save_artist();
      show_artist_form($id);
}elseif(isset($_GET['artist'])){
      show_artist_form($_GET['artist']);
}else{
      show_artist_list();
}

function show_artist_list(){
      $sql="SELECT artist_id,name FROM artists ORDER BY name";
      $res=sql($sql);
      print("<h1>Artist List</h1>");
      while($row=row($res)){
            print("<a href=\"?artist=".urlencode($row['artist_id'])."\">".htmlspecialchars($row['name'])."</a><br/>");
      }
      print("<a href=\"?artist=\"><b>add new</b></a>");
}

function show_artist_form($artist=NULL){
      $artist_styles=array();
      $name="";
?>
  <script>
     function formstatus(s){
        if(s){
           document.forms['f'].elements['save'].disabled=false;
           document.forms['f'].elements['cancel'].value="cancel";
           document.getElementById('msg').innerHTML='&nbsp;';
        }else{
           document.forms['f'].elements['save'].disabled=true;
        }
     }
  </script>
<?php
      
      if($artist){
            $sql="SELECT name FROM artists WHERE artist_id=".esc($artist);
            $res=sql($sql);
            if(num($res)){
                  $row=row($res);
                  $name=$row['name'];
            }else{
                  die("artist not found");
            }
            print("<h1>".htmlspecialchars($name)."</h1>");
            
            $artist_styles=artist_styles($artist);
      }else{
            print("<h1>New artist</h1>");
      }
      
      print("<div style=\"color:green\" id=msg>");
      if(isset($_POST['save'])){
            print("Your changes were saved!");
      }else{
            print("Make your changes then click 'save'");
      }
      print("</div>");
      
      print("<form name=f method=POST action=\".\">");
      print("<input type=hidden name=artist value=\"".htmlspecialchars($artist)."\" onchange=\"formstatus(1)\">");
      print("<input name=\"name\" value=\"".htmlspecialchars($name)."\" onchange=\"formstatus(1)\"><br/>");
      
      $sql="SELECT style_id,name FROM styles ORDER BY name";
      $res=sql($sql);
      while($row=row($res)){
            print("<input type=checkbox name=\"styles[]\"");
            if(in_array($row['style_id'],$artist_styles)){
                  print(" checked");
            }
            print(" value=\"".htmlspecialchars($row['style_id'])."\" onclick=\"formstatus(1)\">");
            print(" ".htmlspecialchars($row['name'])."<br/>");
      }
      
      print("<input type=submit name=save value=save>");
      print("<input type=button name=cancel value=\"back to list\" onclick=\"location='.'\">");
      print("</form>");

      print("<script>formstatus(0)</script>");
      if(isset($_POST['save'])){
            print("<script>document.forms['f'].elements['cancel'].value='back to list'</script>");
      }


}


function save_artist(){
      $id=$_POST['artist'];
      
      if(!$_POST['name']){
            die("Artist name not entered");
      }
      
      if($id){
            $sql="UPDATE artists SET name=".esc($_POST['name'])." WHERE artist_id=".esc($id);
            $res=sql($sql);
      }else{
            $sql="INSERT INTO artists(name) VALUES(".esc($_POST['name']).")";
            $res=sql($sql);
            $id=insid();
      }
      
      if(isset($_POST['styles'])){
            $selected_styles=$_POST['styles'];
      }else{
            $selected_styles=array();
      }
      
      $artist_styles=artist_styles($id);
      
      $sql="SELECT style_id FROM styles ORDER BY name";
      $res=sql($sql);
      while($row=row($res)){
            $current_style=$row['style_id'];
            if(
                in_array($current_style,$selected_styles)
              && !in_array($current_style,$artist_styles)
            ){
                  add_artist_style($id,$current_style)
                    or myerror("Couldn't add style to artist");
            }elseif(
                !in_array($current_style,$selected_styles)
              && in_array($current_style,$artist_styles)
            ){
                  remove_artist_style($id,$current_style)
                    or myerror("Couldn't remove style from artist");
            }
      }
      
      return $id;      
      
}
      

function artist_styles($artist){
      $artist_styles=array();
      $sql="SELECT style_id FROM artist_style WHERE artist_id=".esc($artist);
      $res=sql($sql);
      while($row=row($res)){
            $artist_styles[]=$row['style_id'];
      }
      return $artist_styles;
}

function add_artist_style($artist,$style){
      $sql="INSERT INTO artist_style(artist_id,style_id) VALUES(".esc($artist).",".esc($style).")";
      return sql($sql);
}

function remove_artist_style($artist,$style){
      $sql="DELETE FROM artist_style WHERE artist_id=".esc($artist)." AND style_id=".esc($style);
      return sql($sql);
}
            
function esc($str){
      return "'".mysql_escape_string($str)."'";
}

function sql($sql){
      global $DB;
      return mysql_query($sql,$DB);
}

function row($res){
      if($res){
            return mysql_fetch_assoc($res);
      }else{
            return false;
      }
}

function num($res){
      return mysql_num_rows($res);
}

function insid(){
      global $DB;
      return mysql_insert_id($DB);
}

function myerror($str){
      die($str.": ".mysql_error());
}

To town you have gone... :)

Oh wow. I'm so smart! :x Thanks ThG... I obviously didn't deserve those. I had an email saying "Good Assist" today, and I was thinking... I never gave any answers :)

Lance

Thanks, ThG!