php中生成树形菜单

废话不多说！上代码

class tree
 {
  /**
  * 生成树型结构所需要的2维数组
  * @var array
  */
  var $arr = array();

 /**
  * 生成树型结构所需修饰符号，可以换成图片
  * @var array
  */
  var $icon = array('│','├','└');

 /**
  * @access private
  */
  var $ret = '';

 /**
  * 构造函数，初始化类
  * @param array 2维数组，例如：
  * array(
  *      1 => array('id'=>'1','parentid'=>0,'name'=>'一级栏目一'),
  *      2 => array('id'=>'2','parentid'=>0,'name'=>'一级栏目二'),
  *      3 => array('id'=>'3','parentid'=>1,'name'=>'二级栏目一'),
  *      4 => array('id'=>'4','parentid'=>1,'name'=>'二级栏目二'),
  *      5 => array('id'=>'5','parentid'=>2,'name'=>'二级栏目三'),
  *      6 => array('id'=>'6','parentid'=>3,'name'=>'三级栏目一'),
  *      7 => array('id'=>'7','parentid'=>3,'name'=>'三级栏目二')
  *      )
  */
  function tree($arr=array())
  {
        $this->arr = $arr;
     $this->ret = '';
     return is_array($arr);
  }

    /**
  * 得到父级数组
  * @param int
  * @return array
  */
  function get_parent($myid)
  {
   $newarr = array();
   if(!isset($this->arr[$myid])) return false;
   $pid = $this->arr[$myid]['parentid'];
   $pid = $this->arr[$pid]['parentid'];
   if(is_array($this->arr))
   {
    foreach($this->arr as $id => $a)
    {
     if($a['parentid'] == $pid) $newarr[$id] = $a;
    }
   }
   return $newarr;
  }

    /**
  * 得到子级数组
  * @param int
  * @return array
  */
  function get_child($myid)
  {
   $a = $newarr = array();
   if(is_array($this->arr))
   {
    foreach($this->arr as $id => $a)
    {
     if($a['parentid'] == $myid) $newarr[$id] = $a;
    }
   }
   return $newarr ? $newarr : false;
  }

    /**
  * 得到当前位置数组
  * @param int
  * @return array
  */
  function get_pos($myid,&$newarr)
  {
   $a = array();
   if(!isset($this->arr[$myid])) return false;
         $newarr[] = $this->arr[$myid];
   $pid = $this->arr[$myid]['parentid'];
   if(isset($this->arr[$pid]))
   {
       $this->get_pos($pid,$newarr);
   }
   if(is_array($newarr))
   {
    krsort($newarr);
    foreach($newarr as $v)
    {
     $a[$v['id']] = $v;
    }
   }
   return $a;
  }

    /**
  * 得到树型结构
  * @param int ID，表示获得这个ID下的所有子级
  * @param string 生成树型结构的基本代码，例如："<option value=$id $selected>$spacer$name</option>"
  * @param int 被选中的ID，比如在做树型下拉框的时候需要用到
  * @return string
  */
  function get_tree($myid, $str, $sid = 0, $adds = '', $str_group = '')
  {
   $number=1;
   $child = $this->get_child($myid);
   if(is_array($child))
   {
       $total = count($child);
    foreach($child as $id=>$a)
    {
     $j=$k='';
     if($number==$total)
     {
      $j .= $this->icon[2];
     }
     else
     {
      $j .= $this->icon[1];
      $k = $adds ? $this->icon[0] : '';
     }
     $spacer = $adds ? $adds.$j : '';
     $selected = $id==$sid ? 'selected' : '';
     @extract($a);
     $parentid == 0 && $str_group ? eval("$nstr = "$str_group";") : eval("$nstr = "$str";");
     $this->ret .= $nstr;
     $this->get_tree($id, $str, $sid, $adds.$k.' ',$str_group);
     $number++;
    }
   }
   return $this->ret;
  }
     /**
  * 同上一方法类似,但允许多选
  */
  function get_tree_multi($myid, $str, $sid = 0, $adds = '')
  {
   $number=1;
   $child = $this->get_child($myid);
   if(is_array($child))
   {
       $total = count($child);
    foreach($child as $id=>$a)
    {
     $j=$k='';
     if($number==$total)
     {
      $j .= $this->icon[2];
     }
     else
     {
      $j .= $this->icon[1];
      $k = $adds ? $this->icon[0] : '';
     }
     $spacer = $adds ? $adds.$j : '';

     $selected = $this->have($sid,$id) ? 'selected' : '';
     //echo $sid.'=>'.$id.' : '.$selected.' . <br/>';
     @extract($a);
     eval("$nstr = "$str";");
     $this->ret .= $nstr;
     $this->get_tree_multi($id, $str, $sid, $adds.$k.' ');
     $number++;
    }
   }
   return $this->ret;
  }

  function have($list,$item){
   return(strpos(',,'.$list.',',','.$item.','));
  }
 }