Thanks, it works perfectly!
Only one more question: if I have multiple selections in checkboxes, how can I use the implode correctly? At the moment I tried this:
$myArray = array();
foreach($choices as $value => $label) {
if (in_array($value, $field_value)) {
$myArray[] = "<a href='$value'>$label</a>";
echo implode( ', ', $myArray);
} }
But it kind messes something up.