Hi,
You're right, it can be done through custom php and a 'After Store field plugin' : http://www.seblod.com/products/1854
there's a CCK php class that lets you create custom content.
The 'create' method has 3 parameters :
1st is the content type name (not title)
2nd is an array of values indexed by the Joomla object column names (#__content, #__categories or #__users)
3rd is an array of values indexed by the CCK content type column names
In this example, we just fill the basic Joomla article fields and a cck field value which would link Content A & B
This field would be configured to process a php file containing this piece of code :
<?php defined('JPATH_BASE') or die;
$app=JFactory::getApplication();
$db=JFactory::getDBO();
$content_a=new JCckContent( $config['id'] );
if ($config['isNew']) { //Content A is new
$content_b = new JCckContent( array('joomla_article') );
$status=$content_b->create(
'content_type_b_name',
array(
'title'=> $content_a->get('title') . ' - Content B',
'catid'=>##,
'state'=>1,
'language'=>'*',
'publish_up'=>JFactory::getDate()->toSql(),
'created_by'=>$content_a->get('created_by'),
'access'=>$content_a->get('access')
),
array(
'content_a_id'=>$custom_view->get('id'),
...
)
} else { //Content A has been updated
//Actions on content A update
}
Olivier