Listing Cities not in Database in CakePHP

Question

I have an application in CakePHP that lists businesses. I have a business model/controller, as well as a state_list model/controller. However I want to be more detailed so when a user clicks on a State page, it lists all the cities in that particular State that businesses are listed in.
Then when they click a particular city it then shows a page listing all the businesses in that particular city.

How would I be able to do this without a database table of a listing of all cities?

Answer 1

For this purpose a better database structure would be something along the lines of this:

Table: Location
id
parent_id
name
type

Table: Business
id
location_id
...

Your cities and states should form a tree:

America
   California
      San Francisco
   New York
      ...
Japan
   Tokyo
      ...

For example:

Business ( ..., location_id => 5, ... )
Location ( id => 5, parent_id => 2, name => San Francisco, type => city )
Location ( id => 2, parent_id => ..., name => California, type => state )

That way each business belongs to a city and implicitly to a state and a country as well and everything has a nice id. You also can't make the mistake of having a business that's in New York, California, Japan (which is currently possible).

Given what you have you can only filter cities via a name search:

$listOfBusinessesInState = $this->Business->find('all', array(
    'conditions' => array('Business.state_id' => $state_id),
    'fields'     => array('Business.city'),
    'group'      => array('Business.city')
));
$listOfCitiesInState = Set::extract('/Business/city', $listOfBusinessesInState);