PHP使用递归生成文章树

function category_tree($fatherid){  //require_once("mysql_class/config.inc.php");  //require_once("mysql_class/Database.class.php");  $db = new Database(DB_SERVER, DB_USER, DB_PASS, DB_DATABASE);  $db->connect();  $sql = "SELECT id,title,url FROM ".TABLE_TASK."      WHERE fatherid=$fatherid and ispublic=1 order by id asc";  $articles = $db->query($sql);  $db->close();  while ($record = $db->fetch_array($articles)){    $i = 0;    if ($i == 0){      if($fatherid==0){        echo '<ul class="article-list-no-style border-bottom">';      }else{        echo '<ul class="article-list-no-style">';      }          }    if($fatherid==0){      echo '<li><span class="glyphicon glyphicon-log-in"       aria-hidden="true" id="han'.$record['id'].'">      </span>  <a href="'.$record['url'].'" target="_blank">'       . $record['title'].'</a>';    }else{      echo '<li><span class="glyphicon glyphicon-chevron-right" aria-hidden="true">      </span> <a href="'.$record['url'].'" target="_blank">'       . $record['title'].'</a>';    }        category_tree($record['id']);    echo '</li>';    $i++;    if ($i > 0){      echo '</ul>';    }  }}

category_tree(0) //先提取最顶层文章