PHP implode is exploding my mind!!!!!!

[Antivirus]

What i want to do: pull all forum ids having a specific parent forum, and place them in a string ( $newsfeedforumids ) so they can be added to end of external.php lilke this:

PHP Code:

$vboptions[bburl]/external.php?type=rss2&forumids=$newsfeedforumids 


My query:

PHP Code:

// set parent forum id
$parentid = 6;

// get child forumids for parent
$forumids_q = $db->query_read("
    SELECT forumid 
    FROM " . TABLE_PREFIX . "forum 
    WHERE parentid = $parentid
");
$forumids = mysql_fetch_array($forumids_q);
$newsfeedforumids = implode(",", $forumids); 


Then I plug the $newsfeedforumids onto the end of external.php llike so:

<a href="$vboptions[bburl]/external.php?type=rss2&amp;forumids=$newsfeedforumids" target="_blank">Click for Feed</a>

however there's 14 different forum ids supposed to be queried, and all i get attached to the end of the url is the first result as so:
bburl/external.php?type=rss2&forumids=7,7

What am i doing wrong?