PHP showing stored checkbox data to an update form

I was wondering if anyone could help, I am creating an update product form which is showing results of data already in the database. I want to display all the checkbox categories and have the ones that have already been selected as checked so the user can easily select and change.

I know I am overcomplicating the code below but I am really no sure how to go about this. The code below currently selects all the categories and displays them as checkboxes but I cant get it to display the ones the user开发者_如何学JAVA has already selected and saved to the db as checked. Also I am using MySQL original version not the improved one which I know I should be but If anyone could help I would really appreciate it Thanks Louise.

<?php

             $query  = "SELECT *  FROM category, catid_productid WHERE catid_productid.product_id ='$product_id' ORDER BY product_id ASC";
             $result = mysql_query($query);

             $query  = "SELECT *  FROM category, catid_productid WHERE category.cat_id = catid_productid.cat_id AND catid_productid.product_id ='$product_id' ORDER BY product_id ASC";
             $selected_result = mysql_query($query);
             $selected_array = array($selected_result);


             while($row = mysql_fetch_array($result, MYSQL_ASSOC))
                {

                    $title= $row ['title'];
                    $cat_id= $row ['cat_id'];
                    echo '<li><label for="category-'.$cat_id.'" id="labelleft">'.$title.'</label>';
                    echo '<input name="category[]" id="category-'.$cat_id.'" type="checkbox" class="formbox" value="'.$cat_id;
                    if (isset($_GET['product_id']) && in_array($selected_array['$selected_result'], $selected_array)) {
                        echo 'checked="checked"';
                    }
                    echo " /></li>'";


                }
             ?>

form field:

<div class="field-row ">
     <label for="categories"> Categories:<?php
            if (isset($required) && in_array('category', $required)) { ?>
            <span class="warning">*</span><?php } ?></label>
            <div class="fields">
            <ul>

             <?php 
             $query  = "SELECT *  FROM category ORDER BY title ASC";
             $result = mysql_query($query);

                while($row = mysql_fetch_array($result, MYSQL_ASSOC))
                {
                    $title= $row ['title'];
                    $cat_id= $row ['cat_id'];
                    echo '<li><label for="category-'.$cat_id.'" id="labelleft">'.$title.'</label>';
                    echo '<input name="category[]" id="category-'.$cat_id.'" type="checkbox" class="formbox" value="'.$cat_id.'" /></li>';
                }
             ?>

            </ul>
  </div>
  </div>

inserting it into the database

if($result) {
            $product_id = mysql_insert_id();

            foreach ($category as $cat_id)
            {
            // connect to mysql database
            mysql_query("INSERT INTO catid_productid (cat_id, product_id) VALUES ('$cat_id', '$product_id')");
            }

I don't know if you store checked-or-not information in your DB but I do spot mis-quotation here ..

Try changing this

echo '<input name="category[]" 
        id="category-'.$cat_id.'" 
        type="checkbox" class="formbox" value="'.$cat_id;

To

echo '<input name="category[]" 
       id="category-'.$cat_id.'" 
       type="checkbox" class="formbox" value="'.$cat_id.'"';

AND this

echo " /></li>'";

to

echo ' /></li>';