How to theme an element of an array? - drupal

Question

I have this array in a Drupal 7 installation, it outupts the term list that belongs to a specific vocabulary id:
<?php print render($content['taxonomy_vocabulary_3']); ?>
Now, what this does it outputs the result in a list, I would like to output it in a comma separated line.
Now, I suppose that I could do that with a foreach statement?
I´ve tried this, after reading the documentation, but it outputted nothing:
foreach($taxonomy_vocabulary_3 as $id=>$tag) {
echo "$tag, " ;
}
I´ve looked into what the Devel module told me about that array, and it showed me this:
taxonomy_vocabulary_3 (Array, 1 element)
und (Array, 2 elements)
0 (Array, 1 element)
tid (String, 3 characters ) 141
1 (Array, 1 element)
tid (String, 3 characters ) 320
But as you can see it shows the term id in each case, and not the term name...
What do you suggest? Thanks!!

Answer 1

You can load the term and then print it's title.
foreach($vocabulary as $tid) {
$term = taxonomy_term_load($tid);
// print whatever you want from this object.
print $term->title . ', ';
}
taxonomy_term_load

Answer 2

What you got is a build array - so that means that
$content['taxonomy_vocabulary_3']['#theme']
will be the theme function used to render the vocabulary. If you want to change the output you have two good solutions.
override the standard theme function in your theme - this will alter the output of all the calls to that theme function - in this case how all vocabularies is rendered.
Change the #theme value to a theme function of your liking - this could be a custom theme function you define in your theme.
For help on how to render the terms, you can take a look at how the original theme function is implemented - you can look it up at the Drupal API documentation.