Create “nested” string from multidimensional array

I need to convert a multidimensional array of sql where statements to a string with the correct operators and parenthesizes. I want to end up with a string that looks like this:

WHERE (author_id=1 || author_id=2) && status=1

The key here is that I need to create a "nested" string, i.e. have conditionals in my string wrapped with parenthesizes at the right spots.

It seems easy enough, but I am wool-headed today and can't come up with anything other than the below - and it feels like poor design.

Short explanation - How to convert the following array into the above, with any kind of links between filters

$aFilters[$filter_id] = array(
    'field' => $field,
    'value' => $value,
    'operator' => $operator, /** = or != */
    'link_id' => $another_filter_id,
    'link_operator' => $link_operator, /** && or || */
);

Long explanation (My attempt)

1. I have a method for assigning new filters. $search->addFilter($fieldname, $value, $operator, $fieldLinkId, $fieldLinkOperator);
2. I then create two arrays based on this.
   • $filters - This contains the raw data from the addFilter() method, with the array key as filter ID
   • $filterMap - This contains a map of all filter IDs and their children. i.e [1] => {2,3,4} (filter 1 is linked to filter 2,3 and 4)

3. I then have a very ugly recursive function to create my string (below)

   private function buildCriteriaStringSection($aFilters, $aFilterMap, $aFilterID = 0)
   { 
       $bHasChildrenLinks = isset($aFilterMap[$iFilterID]);
       $str = $aFilters[$iFilterID]['link_operator'];
       $str .= (($bHasChildrenLink && $iFilterID != 0) ? '(' : '');
       $str .= $aFilters[$iFilterID]['field'] . $aFilters[$iFilterID]['operator'] . $aFilters[$iFilterID]['value'];
       if($bHasChildrenLinks) {
           foreach($aFilterMap[$iFilterID] as $key => $iChildFilterId) {
               $str .= $this->buildCriteriaStringSection($aFilters, $aFilterMap, $iChildFilterId);
           }
       }
       return $str .= ($bHasChildrenLinks && $iFilterID != 0 ? ')' : '');
   }
   

4. At the very last I even have to trim off some operators that have been added due to to the structure above $str = ltrim($this->buildCriteriaString(), '&|=');

So how do I make this more sophisticated?