PHP var_export - elgg_get_entities - php

Question

I am trying to create an API for the social network Elgg. It's working but I am very puzzled by some results.
This is my API:
function my_get_group() {
$group=elgg_get_entities(array(
types => 'group',
guid=>75,
));
return var_export($group[0], true);
}
and this is the reult
{
status: 0
result: "ElggGroup::__set_state(array( 'url_override' => NULL, 'icon_override' => NULL, 'temp_metadata' => array ( ), 'temp_annotations' => array ( ), 'temp_private_settings' => array ( ), 'volatile' => array ( ), 'tables_split' => 2, 'tables_loaded' => 2, 'attributes' => array ( 'guid' => 75, 'type' => 'group', 'subtype' => 0, 'owner_guid' => 54, 'site_guid' => 1, 'container_guid' => 54, 'access_id' => 2, 'time_created' => 1442385556, 'time_updated' => 1442385557, 'last_action' => 1442455132, 'enabled' => 'yes', 'name' => 'goup1', 'description' => '<p>description1</p>', ), 'valid' => false, ))"}
So far so good.
I can now modify my APIto get only the description, by changing
//return var_export($group[0], true);
return var_export($group[0]->description, true);
which gives me
{
status: 0
result: "'<p>description1</p>'"
}
Now the part that I don't understand is the following. if I modify my code to:
//return var_export($group[0], true);
return var_export($group[0]->briefdescription, true);
I get
{
status: 0
result: "'brief description1'"
}
Can someone explain me where this data comes from? I cannot see any mention of briefdescription when I run
return var_export($group[0], true);
Thanks for your help
bonododo

Answer 1

All of those values come through PHP magic methods __get and __set. The reason you see description in var_export result is that it's an attribute, the briefdescription is a metadata.
Have a look at documentation, especially:
Data model overview
Metadata section
ElggGroup-specific attributes