How to prepopulate a term reference field with multiple values on a new form?

Question

I seem to struggle with a problem which has already been answered. I have a 'review' form on which there is a field that I want to prepopulate. It is a term reference field and I want it to be prepopulated with taxonomy values from another node. I have looked at this issue without success. Any help would be greatly appreciated.

function my_module_form_alter(&$form, &$form_state, $form_id) {
      $nodeid=$_GET['id']; 
      $node=node_load($nodeid);
      if ($form_id == 'review_node_form') {     
        $form['field_revactivities']['und'][0]['value']['#default_value'] = $node->field_ad_tags['und'][0]['tid'];
      }
}

I know that '$node->field_ad_tags['und'][0]['tid']' returns the number of the term, but I am not sure how to get the value into the new field.

Also, if there are multiple terms for the field, should I populate the field for each term by incrementing [0], then ['1'], etc...?

Answer 1

Answering my own question: 1) First aspect is to feed the data correctly to the term reference field. The magic formula I found is:

$form['field_revactivities'][LANGUAGE_NONE]['#default_value'] = array($bidule);

where $bidule is a the string of taxonomy term (not its taxonomy id).

2) If there are multiple elements in the field_ad_tags, then I had to create a loop to place them all one after the other in a string. It was important to have the exact wording of each taxonomy term for the field to recognise which tag it is and to separate them with a comma. Here is my final code:

$bidule = '';
$i=0;
foreach ($node->field_ad_tags['und'] as $truc => $value) {
        drupal_set_message('<pre>$truc '. print_r($value, TRUE) .'</pre>');
        $term = taxonomy_term_load($node->field_ad_tags['und'][$i]['tid']);
        $name = $term->name;
        $bidule= $bidule.','.$name;
        $i++;
}
$bidule=substr($bidule, 1); // Remove the first character ','

$form['field_revactivities'][LANGUAGE_NONE]['#default_value'] = array($bidule);