PHP - Modify What Database Fields Are Searched

Hi all,
I'm brand new to php / mysql and I'm trying to modify this script which currently runs a search on two fields "product_number" and "product_name". I also want the search to consider a third field "product_type". When I remove either product_name or product number from the following part of the code, it removes that field from being considered in the search: Code: [Select]
$search_map = array($orderby, 'product_number','product_name',);
So shouldn't I be able to just add the third field's name to this array and have it be considered too? I'm a complete beginner so I'm hoping this is a simple fix and I just dont get it.

Here's the rest of what I think is the relevant code:
Code: [Select]
function load_all_products()
{
    global $AppUI;
    global $sorted_item_list;
    global $additional_pfilter;
    load_type_list();
    $orderby = 'product_id';
    $search_map = array($orderby, 'product_number','product_name',);
    $where = $AppUI->getState( 'QuoteIdxWhere' ) ? $AppUI->getState( 'QuoteIdxWhere' ) : '*';
    $not =" ";
    $op =  " OR";
    $check = substr(trim($where),0,4);
    if(stristr($check,"NOT")){
        $op ="AND";
        $not = " NOT ";
        $where = substr(trim($where),4);
        $where = trim($where);
    }

    // assemble the sql statement
    $q = new DBQuery;
    $q->addTable('products');
    $q->addJoin('companies', 'com', 'products.product_company_id = com.company_id');
    $q->addJoin('users', 'u', 'products.product_owner = u.user_id');
    $q->addQuery('products.*, com.company_name, u.user_username');
    $where_filter = " ";
    foreach($search_map as $search_name)
        $where_filter .=" $op $search_name $not REGEXP '$where'";
    $where_filter = substr($where_filter, 5);
 //   echo $where_filter;
    if($where != "*")
       $q->addWhere("($where_filter)");
    $q->addOrder('product_id');

    $sql = $q->prepare();
    $q->clear();
    $sql_list = db_exec( $sql );
    if ($sql_list)
  $rn = db_num_rows( $sql_list );
    else {
   echo db_error();
   $rn = 0;
    }

$product_list = array();
    foreach ($sql_list as $item)
{

$product_list[ $item[ 'product_id' ] ] = $item;

}

// sort the list

global $sort_state;
if ( !isset( $sort_state ) ) $sort_state = getProductSortState();

if ( isset( $sort_state[ 'sort_item1' ] ) )
{
if ( isset( $sort_state[ 'sort_item2' ] ) )
{
$sorted_item_list = array_csort2( $product_list, $sort_state['sort_item1'], intval( $sort_state['sort_order1'] )
, $sort_state[ 'sort_item2' ], intval( $sort_state['sort_order2'] ) );
}
else
{
$sorted_item_list = array_csort2( $product_list, $sort_state['sort_item1'], intval($sort_state['sort_order1']) );
}
}
else $sorted_item_list = array_csort2( $product_list, 'product_id' );

}
Thanks!