function buildCategoryOptionTree($id, $depth=0, $html="")
{	
	global $mysql;
	
	$thisCategory = $mysql->query("SELECT * FROM `categories` WHERE `id`='$id'");
	$data = $thisCategory->fetchArray();
	
	$html .= "<option value=\"".$data['id']."\">";
		
	if($depth > 0)
	{			
		if($depth > 1)
			for($i=0;$i<$depth;$i++)
				$html .= "&nbsp;&nbsp;";
			
		$html .= "&#9492;&nbsp;";
	}
	
	$html .= $data['name']."</option>\n";

	$subcategories = $mysql->query("SELECT * FROM `categories` WHERE `parent_id`='$id'");
	
	if($subcategories->numRows > 0)
	{
		$depth++;
		
		while($row = $subcategories->fetchArray())
		{
			$html .= buildCategoryOptionTree($row['id'], $depth, $html);
		}
	}

	return $html;
}


$result = $mysql->query("SELECT * FROM `categories` WHERE `parent_id`='0' ORDER BY `name`");

while($row = $result->fetchArray())
{												
	$categoriesHTML .= buildCategoryOptionTree($row['id'], null);
}