[...]

if( PEAR::isError( $news_res = &$this->db->query($sql) ) ) {
  die($news_res->getMessage());
}
			
$newsArr = array();
		
//Walk trough all news
while($news_res->fetchInto($news_row)) {
/* Array auslesen bla bla */

  /* Alle Kategorien, zu der der Eintrag gehört, ermitteln */
  $cat_sql = "SELECT cat_id FROM cat_to_news WHERE news_id = '" . $news_row[1] . "'";
										
  if( PEAR::isError( $cat_res = &$this->db->query($cat_sql) ) ) {
    die($cat_res->getMessage());
  }
				
  $catArr = array();
				
  //Write all categorie_ids in an array
  while($cat_res->fetchInto($cat_row)) {
    array_push($catArr, $cat_row[0]);
  }
				
  $tmpArr['categorie_ids'] = $catArr;
				
  array_push($newsArr, $tmpArr);
				
}

[...]