CakePHP v2.x

1. Install this plugin for your CakePHP app.
   Assuming APP is the directory where your CakePHP app resides, it's usually app/ from the base of CakePHP.

   cd APP/Plugin
   git clone git://github.com/LubosRemplik/CakePHP-Magento-API-Plugin.git Magento

2. Set up datasource, example is in Magento/Config/database.php.default (you need to get api user and key in magento admin panel).

3. Include needed model in your controller or anywhere you want to

   $uses = array('Magento.CategoryProduct');
   ...
   $data = $this->CategoryProduct->listWithInfo();
   debug ($data);

   $data = ClassRegistry::init('Magento.CategoryProduct')->listWithInfo();
   debug ($data);