title: cakephp HABTM same model
body: <p>I have a site develop in cakephp 2.0
  I want to make a HABTM relation to the same model: A product can has more products.</p>
  
  <p>I thinked to do in this mode into my model:</p>
  
  <pre><code>class Product extends AppModel {
      public $name = 'Product';
      public $useTable = 'products';
      public $belongsTo = 'User';
      public $actsAs = array('Containable');
  
          public $hasAndBelongsToMany = array(
          'Ingredient' =&gt; array(
              'className' =&gt; 'Product',
              'joinTable' =&gt; 'ingredients_products',
              'foreignKey' =&gt; 'product_id',
              'associationForeignKey' =&gt; 'ingredient_id', 
              'unique' =&gt; true
          )
      );
  
  } 
  </code></pre>
  
  <p>Is correct my relation? But have I to insert into my table products  the field product_id and ingredient_id?
  And how can I save my data with a form? I know how to save data with HABTM but I never done an HABTM to the same table. </p>