Sınırsız alt kategorili menüde sorun

function category_list( $bag_id = 0 )
{

// build our category list only once
static $cats;

if ( ! is_array( $cats ) )
{

$sql = 'SELECT * FROM `urunler_kategori`';
$res = mysql_query( $sql );
$cats = array();

while ( $cat = mysql_fetch_assoc( $res ) )
{
$cats[] = $cat;
}

}

// populate a list items array
$list_items = array();

foreach ( $cats as $cat )
{

// if not a match, move on
if ( ( int ) $cat['bag_id'] !== ( int ) $bag_id )
{
continue;
}

// open the list item

$list_items[] = '

';

// construct the category link
$list_items[] = '';
$list_items[] = $cat['baslik'];
$list_items[] = '';

// recurse into the child list
$list_items[] = category_list( $cat['id'] );

// close the list item
$list_items[] = '

';

}

// convert to a string
$list_items = implode( '', $list_items );

// if empty, no list items!
if ( '' == trim( $list_items ) )
{
return '';
}

// ...otherwise, return the list
return '

' . $list_items . '

';

}

echo category_list();
?>