I am very new to php/mysql and this is causing me to loose hairs, I am trying to build a multi level site navigation. In this part of my script I am readying the sub and parent categories coming from a form for insertion into the database:

        // get child categories

        $catFields = $_POST['categories'];

        if (is_array($catFields)) {

            $categories = $categories;

                for ($i=0; $i<count($catFields); $i++) {

                    $categories = $categories . $catFields[$i]";

                }

            }

// get parent category

$select = mysql_query ("SELECT parent FROM categories WHERE id = $categories");

while ($return = mysql_fetch_assoc($select)) {

     $parentId = $return['parent'];

}

The first part of my script works fine, it grabs all the categories that the user has chosen to assign a post by checking the checkboxes in a form and readies it for insertion into the database.

But the second part does not work and I can't understand why. I am trying to match a category with a parent that is stored in it's own table, but it returns nothing even though the categories all have parents. Can anyone tell me why this is?

p.s. The $categories variable contains the sub category id.