I have a table column called post_tags within a table called posts where assigned tags are stored separated by the @ symbol. I also have a table called tags where all tag names are stored. I would like to design my database in a more normalized way but for the purpose I am trying to achieve this is the easiest option.

Anyway, I want to display on the screen all the entries from the tags table as checkboxes, so I do:

    $query = mysql_query("SELECT * FROM tags ORDER BY name");

    while ($row = mysql_fetch_assoc($query)) {

        $tag = $row['name'];

        echo "<input type='checkbox' name='tags[]' value='$tag' />\n";

    }

Next I want to have the tags that are assigned to a particular post be preselected. For example, if I have a post with the following in it's post_tags column:

party@beaches@dolphins@

I want the "party", "beaches" and "dolphin" checkboxes to be checked by default (while the checkboxes for the other options are unchecked). How can this be done?