How to get entityreference_backreference data programmatically

Question

The User profile for my site contains the Entity Reference field 'Parent' which points to another User.

I have the entityreference_backreference module enabled on my Drupal 7 site. I need to programmatically access the values of the properties added to the user entity by the entityreference_backreference module, so that for User A, I can identify all other Users which point to A via the 'Parent' EntityReference field.

If I do the following

$wrapper = entity_metadata_wrapper("user",$some_user);
$wrapper->getPropertyInfo();

I can see that that an entry for the entityreference_backreference field field_parent_user_eb is available in the getPropertyInfo() output. So the property does exist.

However, if I do

$wrapper->get('field_parent_user_eb');

it comes back with "data = null".

Also if I just try to access $some_user->field_parent_user_eb that also gives a null result.

It looks like the property is never being set.

What am I doing wrong? I can see that there is a "getter callback" defined for the field_parent_user_eb property, which is set to entityreference_backreference_related_entities, but I can't see how I can use this.

Any help much appreciated!

Answer 1

OK this was my ignorance of how to use Entity Metadata Wrappers. The way to get the value of the field_parent_user_eb field is

$wrapper = entity_metadata_wrapper("user",$some_user);
$value = $wrapper->field_parent_user_eb->value();

$value contains an array of entities which (back) reference the original $some_user.

I should have read https://www.drupal.org/docs/7/api/entity-api/entity-metadata-wrappers before posting.