How to show all locations with a parent id

pp4sale

What would be the easiest way to show all locations with a parent id.

To explain I have multiple locations within countries.

I want a link which will show all locations in a country, eg all counties in England. England has the parent id of "18" and the counties have id's from 1 to 40.

If someone clicked on "show all listings in England" to show all listings in England.

Can I just add all the id's to this in MYSQL or is there something I can change to the php code?

Thanks in advance...

This is the code:

{if isset($location)}{$location.title}{else}{$lang.choose_location}{/if}</strong>
</span>
(<a href="#" onclick="return false;"><span id="locationChangeLabel"></span></a>)
</legend>

and

$eSyndiCat->setTable('locations');
$locations = $eSyndiCat->all("*", "`id_parent` = :id", array('id' => $aLocation));

foreach($locations as $key => $location)
{
	$div = '';

	$subcategories = $eSyndiCat->all("*", "`id_parent` = '{$location['id']}'");

	$tree .= "<option value=\"{$location['id']}\">";

	$level = count(explode('/', $location['path']));

		}

function getTree($locationId = 0)
{
global $eSyndiCat;

$out = array();

$eSyndiCat->setTable('locations');
$locations = $eSyndiCat->all('*', "`id_parent` = :id order by `title`", array('id' => $locationId));//Fix