How do you save an entity reference value programmatically?

Question

I am using organic groups, which creates an entity reference field on a content type. Now i have a custom module that is supposed to create a node programatically and i am having trouble with saving the entity reference field.

Error message i get:Notice: Undefined property: DatabaseStatementBase::$nid

Here is what i have tried:

$qry= db_select('node', 'n')
           ->condition('type', 'some_og_content_type', '=') 
           ->condition('title', 'some_title', '=')
           ->fields('n', array('nid'));
$ogRef= $qry->execute();

$ogNid = $ogRef->nid;

$node->og_group_ref['und'][0] = array('target_id'=>$ogNid);

//i also tried this
$node->og_group_ref['und'][0]['target_id']=$ogNid;

Answer 1

You need to get the results of your query after $query->execute() by for example calling $query->fetchAssoc() or $query->fetchAllAssoc(..).

Using $node->og_group_ref[LANGUAGE_NONE][0]['target_id'] is correct.

Be aware of the fact that your query might have multiple results. Do something like this to traverse them all:

$result = $query->execute();
while($entry = $result->fetchAssoc()) {
  $node = node_load($entry['nid']);
  // set the field and save the node
}

Depending on the number of expected entries you could also use EntityFieldQuery explained here https://www.drupal.org/node/1343708.

Another edit: When you want to set a field on a newly created node better use hook_node_presave or hook_node_insert then you do not need to care about searching for your node.