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.","));
  }
 }