I needed to have many subclasses inherited from a main class.

To do that with propel, you need to have all your classes in one big table. I wanted to have separate tables.

Then I discovered the propel behaviors and it does that very well !

Let's see an example with a master class "element" and a subclass "subElement" :

• The tables of the subclasses just need to have an "element_id" foreign key column, to be linked with the "element" master class table :

  # schema.yml example
   
  propel:
  # master class
    element:
      _attributes: { phpName: Element }
      id:
      name:       varchar(255)
      content:     longvarchar
      created_at:
  # subclass with only the subclass properties and element_id foreign key column
    sub_element:
      _attributes: { phpName: SubElement }
      element_id:
      author:      varchar(255)
   

• Activate the behaviors in "project/config/propel.ini" (before building the model!):

  propel.builder.AddBehaviors = true
   

• Don't forget to rebuild the model, anytime you modify it :

  >symfony propel-build-model
   

• Create your behavior in "project/config/config.php" :

  // get propel behavior lib
  require_once($sf_symfony_lib_dir.'/addon/propel/sfPropelBehavior.class.php');
   
  // declare all the methods from of the master class "element", that you'll need in the subclasses
  sfPropelBehavior::registerMethods('ElementBehavior',
    array(
      array('ElementBehavior', 'setName'),
      array('ElementBehavior', 'getName'),
      array('ElementBehavior', 'setContent'),
      array('ElementBehavior', 'getContent'),
      array('ElementBehavior', 'setCreated'),
      array('ElementBehavior', 'getCreatedAt'),
    )
  );
   
  // Modify save() and delete() master class methods
  // SubElement->save() need to run Element->save()..., and so for SubElement->delete()
  sfPropelBehavior::registerHooks('ElementBehavior',
    array(
      ':save:pre' => array('ElementBehavior', 'preSave'),
      ':delete:pre' => array('ElementBehavior', 'preDelete'),
    )
  );
   

• Declare all these behavior methods in the master class model (here in "project/lib/model/Element.php") :

  // declare this class after the element class
  class ElementBehavior
  {       
   
       /*  Properties Setters */
      public function setName(BaseObject $object, $value) {
              if (!$object->getElement()) $object->setElement(new Element());
              $object->getElement()->setName($value);
      }
      public function setContent(BaseObject $object, $value) {
              if (!$object->getElement()) $object->setElement(new Element());
              $object->getElement()->setContent(value);
      }
      public function setCreatedAt(BaseObject $object, $value) {
              if (!$object->getElement()) $object->setElement(new Element());
              $object->getElement()->setCreatedAt($value);
      }
     /*  Properties Getters */
      public function getId(BaseObject $object) {
              if (!$object->getElement()) $object->setElement(new Element());
              return $object->getElement()->getId();
      }
      public function getName(BaseObject $object) {
              if (!$object->getElement()) $object->setElement(new Element());
              return $object->getElement()->getName();
      }
      public function getContent(BaseObject $object) {
              if (!$object->getElement()) $object->setElement(new Element());
              return $object->getElement()->getContent();
      }
      public function getCreatedAt(BaseObject $object) {
              if (!$object->getElement()) $object->setElement(new Element());
              return $object->getElement()->getCreatedAt();
      }  
   
        /* Element save method called just before SubElement save */
      public function preSave(BaseObject $object) {
              // if element not null...
              if ($object->getElement()) {
                      // save element in his table
                      $object->getElement()->save();
                      // if new element, capture id
                      if ($object->isNew()) $object->setElementId($object->getElement()->getId());
              }
      }
       /* Element delete method called just before SubElement delete */
      public function preDelete(BaseObject $object) {
              // if element not null and not new...
              if ($object->getElement() && !$object->getElement()->isNew()) {
                      // delete element in his table
                      $object->getElement()->delete();
              }
      }
  }       
   

• add the "ElemenBehavior" to all your subclasses (here in" project/lib/model/SubElement.php") :

     sfPropelBehavior::add('SubElement', array('ElementBehavior'));
   

• That's all ! You can test it with a code like this :

  // create subElement
  $test = new SubElement();
  // test on element methods
  $test->setName('test');
  $test->setContent('this is the big test !');
   
  // test also SubElement methods
  $test->setAuthor('mr john smith');
  // save in element table AND in sub_element table ! 
  $test->save();
   
  // capture subElement with id 1
  $test = SubElementPeer :: retrieveByPk(1);
  // delete element and subElement in the two tables
  $test->delete();
   
  // mix criteria for both class
  $c = new Criteria();
  $c->add(ElementPeer :: ID, 1);
  $c->add(SubElementPeer :: AUTHOR, 'mr john smith');
  // get a list of the subElements
  $subElements = SubElementPeer :: doSelectJoinElement(new Criteria());
   

• each time you add a column or a method to the element model, you need to declare it in the behavior to be handled in the subclasses.

  It's a way to go, may be there is a simplier way, but this works well for me...