Highlight already selected items in multiple select box - php

Question

I have 2 tables one 'brand' that stores all the brand names and 'brand_category' that stores all the brand names with their corresponding categories. I have a multiple select box that loads all the items in the 'brand' table when the page loads, but I need to highlight the items that are already submitted by the user previously in the 'brand_category' table with the rest of the brands that are left so that the user knows what are the brands left to be entered in the 'brand_category' table. Below is the code but it doesn't work. Please help to resolve this issue
<div class="selectbox">
<label id="brand" class="brand_label">Brand:</lable>
<?php
echo "<select name='brand' class='cat_brands' multiple>"
<option value='0'>None</option>";
$query = mysql_query("SELECT id, name FROM brand");
while($br_query = mysql_fetch_assoc($query)){
$query_select = mysql_query("SELECT * FROM brand_category WHERE brand_id='".$br_query['id']."'");
while($brnd_select = mysql_fetch_assoc($query_select)){
if($brnd_select['brand_id']==$br_query['id']){
echo "<option style='background-color: red' value='".$br_query['id']."'>".$br_query['name']."</option>";
}
}
}
?>
</div>
The above code only displays the brands entered in the 'brand_category' table rest of the brands are not displayed. I need to display them also.

Answer 1

You forgot to mention else condition inside while loop.Here is the code
<div class="selectbox">
<label id="brand" class="brand_label">Brand:</lable>
<?php
echo "<select name='brand' class='cat_brands' multiple>"
<option value='0'>None</option>";
$query = mysql_query("SELECT id, name FROM brand");
while($br_query = mysql_fetch_assoc($query)){
$query_select = mysql_query("SELECT * FROM brand_category WHERE brand_id='".$br_query['id']."'");
while($brnd_select = mysql_fetch_assoc($query_select)){
if($brnd_select['brand_id']==$br_query['id']){
echo "<option style='background-color: red' value='".$br_query['id']."'>".$br_query['name']."</option>";
}else{
echo "<option value='".$br_query['id']."'>".$br_query['name']."</option>";
}
}
}
?>
</div>

Answer 2

If I have understood your query correctly you are trying to pull out all the brands and to make the ones in the brands_category table to display as selected.
You should better be using MySQL PDO extensions rather than this obsolete method
There are better ways to implement this, e.g. by having just one table or by using a Join query, anyway... this should work.
<select name='brand' class='cat_brands' multiple>
<option value='0'>None</option>
<?php
$query = mysql_query("SELECT id, name FROM brand");
while($br_query = mysql_fetch_assoc($query))
{
$query_select = mysql_query("SELECT * FROM brand_category WHERE brand_id='".$br_query['id']."'");
if(mysql_num_rows($query_select) > 0)
{
while($brnd_select = mysql_fetch_assoc($query_select))
{
echo "<option style='background-color: red' value='".$br_query['id']."' selected='selected'>".$br_query['name']."</option>";
}
}
else
{
echo "<option style='background-color: yellow' value='".$br_query['id']."'>".$br_query['name']."</option>";
}
} ?>
</select>