Add items to new category

Currently I am using a script to insert item in an 'items' table and a seperate script to add categories to the 'categories' table. The items table has a field called cat_id and references an id field in the categories table. I need to use a drop down box so that cat_title is displayed from 'categories' but a cat_id is inserted. Here is the code I am using now. Unfortunately if I use a new category with no items the new cat_id is assigned as zero.
<?
$dbcnx = @mysql_connect( "host", "test", "test");
mysql_select_db("testdb");
$query = "SELECT distinct cat_id, cat_title from store_items right join store_categories on store_items.cat_id = store_categories.id";
$result = mysql_query($query);
print "<SELECT name=cat_id>";
while ($line = mysql_fetch_array($result))
{
foreach ($line as $cat_id)

{
print "<OPTION value='$cat_id'";
}
print ">$cat_id</OPTION>";
}

print "</SELECT>";

?>
I am very new to this - any help is greatly appreciated.

Would this be any better? (i.e. get the db to put together the option string?):

- Very helpful - thank you!