无限分类与树型论坛的实现方法
?D?D浮点型字段排序法
Joe Teng 2005.6.12

在此我不想讨论其他实现方法的利与弊。
既然是使用字段排序，那么我们便设一个名为order的字段。问题是，在这里是使用整数还是使用浮点数类型呢？考虑到会有在两个连续order值中间插入新值的可能，自然是需要使用浮点类型了。
建一个menus表，我们还需要以下字段：
id ： 类别编号
mainid ： 主分类编号，但不作具体分类使用。如果在树型论坛里，它代表的是主题id
parentid ： 父类编号
level ： 类别级别，作用其实是方便显示的时候作其他处理
info ： 类别名称等。
由此可以得到menus的表结构：
CREATE TABLE `menus` (
`id` INT( 10 ) UNSIGNED NOT NULL AUTO_INCREMENT ,
`mainid` INT( 10 ) UNSIGNED NOT NULL ,
`parentid` INT( 10 ) UNSIGNED NOT NULL ,
`order` FLOAT UNSIGNED NOT NULL ,
`level` SMALLINT( 5 ) UNSIGNED NOT NULL ,
`info` VARCHAR( 128 ) NOT NULL ,
INDEX ( `mainid` , `parentid` , `order` , `level` ) ,
UNIQUE (
`id`
)
) TYPE = MYISAM ;

很容易可以看出，输入的时候是如此简单便实现树结构了:
SELECT * FROM `menus` ORDER BY `mainid` ASC, `order` ASC ;
前提是添加类别的时候，order能正确排序。

添加根分类：
很简单,取得上一个主类的mainid， 如A_mainid，则新根分类的mainid则为A_mainid + 1。parentid 为 0 ， order 为0， level也为0， info则自行设定。

添加子分类：
核心思想是，取得新增子分类的前一个分类的order以及它后一个分类的order。
取得前一个分类的order是这里的难点，因为涉及到同级与非同级的情况。非同级的情况很简单，新增别类的前一个order其实就是它的父类的order。如果有同级分类，情况就很复杂了，因为它前面的同级分类有可能会拥有子分类，子分类下又可能还会有子分类，如此下来，要取得前一个order就很难了。
解决的办法有两个：
1.取得新增类同级的前一个类别,如类别A的ID，使用递归的方法，直到取得A类别下最后最小分类的order，那便是要新增分类的前一个order了。这种方法的缺点是，如果A类别下有很多子分类，那么递归需要一定的时间。这种方法适用于普通的分类处理，不适用于树型论坛。不过总体来说，因为是添加类别的时候才使用递归，输出类别的时候跟前面一样，效率还是很高的。
2.作一个记录，记录着与A有关联的最后order。于是我们就需要增加一个表，建利关系树。这种关系树做起来很简单。表结构如下：
CREATE TABLE `menu_tree` (
`mainid` int(10) unsigned NOT NULL default '0',
`tree` text NOT NULL,
`order` float unsigned NOT NULL default '0',
KEY `mainid` (`mainid`,`order`),
FULLTEXT KEY `tree` (`tree`)
) TYPE=MyISAM;
(构建方式请看我后面给出的源码)
取得前一个order之后，要取得后一个order就很简单了。取同mainid下大于前一个order的最小order便是了。如果存在后一个order，那么新增order就取前一个order与后一个order的平均值。如果不存在后一个order，那说明新增类别是main下的最小order，取大于前一个order的最小整数就行了。

主要实现方法便如上面说的。

处理方法

<?php
$arrDatabase = array
(
"host" => 'localhost', "user" => 'root', "password" => '123456', "dbname" => 'test'
);

$resDbc = mysql_connect ( $arrDatabase["host"], $arrDatabase["user"], $arrDatabase["password"] );
mysql_select_db( $arrDatabase['dbname'] );

if ( ! class_exists ( "FreeRoad" ))
{
class FreeRoad
{
var $resDbc ;
var $strDatabase ;
var $strMenuTable ;
var $strMenuTreeTable ;

var $strFiled_id = 'id' ;
var $strFiled_mainid = 'mainid' ;
var $strFiled_parentid = 'parentid' ;
var $strFiled_order = 'order' ;
var $strFiled_level = 'level' ;

function FreeRoad ( $resDbc , $strDatabase , $strMenuTable , $strMenuTreeTable , $arrSetFileds = array() )
{
$this->resDbc = $resDbc ;
$this->strDatabase = $strDatabase;
$this->strMenuTable = $strMenuTable ;
$this->strMenuTreeTable = $strMenuTreeTable ;

if ( sizeof ( $arrSetFileds ) > 0 )
{
$this->strFiled_id = $arrSetFileds['id'] ;
$this->strFiled_mainid = $arrSetFileds['mainid'] ;
$this->strFiled_parentid = $arrSetFileds['parentid'] ;
$this->strFiled_order = $arrSetFileds['order'] ;
$this->strFiled_level = $arrSetFileds['level'] ;
}
}

function get_new_mainid ()
{
mysql_select_db ( $this->strDatabase , $this->resDbc ) ;

$strQuery = " SELECT `$this->strFiled_mainid`
FROM `$this->strMenuTable`
WHERE `$this->strFiled_parentid` = 0
ORDER BY `$this->strFiled_id` DESC LIMIT 0 , 1 " ;
$resResult = mysql_query ( &$strQuery , $this->resDbc ) ;
while ( $arrRow = mysql_fetch_array ( $resResult ) )
{
$intLastedMainId = $arrRow[0] ;
}
$intLastedMainId = intval ( $intLastedMainId );
mysql_free_result ( $resResult ) ;
return $intLastedMainId + 1 ;
}

function get_level_lastest_id ( $intParentId )
{
mysql_select_db ( $this->strDatabase , $this->resDbc ) ;
$strQuery = " SELECT `$this->strFiled_id`
FROM `$this->strMenuTable`
WHERE `$this->strFiled_parentid` = $intParentId
ORDER BY `$this->strFiled_id` DESC LIMIT 0 , 1 " ;
$resResult = mysql_query ( &$strQuery , $this->resDbc ) ;
while ( $arrRow = mysql_fetch_row ( $resResult ) )
{
$intLevelLastestId = $arrRow[0] ;
}
mysql_free_result ( $resResult ) ;
return $intLevelLastestId ;
}

function get_level_lastest_order ( $intParentId )
{
mysql_select_db ( $this->strDatabase , $this->resDbc ) ;
$strQuery = " SELECT `$this->strFiled_order`
FROM `$this->strMenuTable`
WHERE `$this->strFiled_id` = $intParentId " ;
$resResult = mysql_query ( &$strQuery , $this->resDbc ) ;
while ( $arrRow = mysql_fetch_row ( $resResult ) )
{
$floSelectItemOrder = $arrRow[0] ;
}
mysql_free_result ( $resResult ) ;

$strQuery = " SELECT `$this->strFiled_order`
FROM `$this->strMenuTreeTable`
WHERE BINARY ( `tree`) LIKE '%|$intParentId|%'
ORDER BY `$this->strFiled_order` DESC LIMIT 0 , 1 " ;
//echo $strQuery ;
$resResult = mysql_query ( &$strQuery , $this->resDbc ) ;
while ( $arrRow = mysql_fetch_row ( $resResult ) )
{
$floSelectItemLastestOrder = $arrRow[0] ;
}
mysql_free_result ( $resResult ) ;
if ( ! $floSelectItemLastestOrder ) $floSelectItemLastestOrder = $floSelectItemOrder ;
return $floSelectItemLastestOrder ;
}

function get_elements ( $intParentId = 0 )
{
mysql_select_db ( $this->strDatabase , $this->resDbc ) ;
if ( $intParentId == 0 )
{
$intMainId = $this->get_new_mainid ( );
return array ( "mainid" => $intMainId , "order" => 0 , "level" => 0 ) ;
}

$strQuery = " SELECT `$this->strFiled_mainid` , `$this->strFiled_order` , `$this->strFiled_level`
FROM `$this->strMenuTable`
WHERE `$this->strFiled_id` = $intParentId " ;
$resResult = mysql_query ( &$strQuery , $this->resDbc ) ;
while ( $arrRow = mysql_fetch_row ( $resResult ) )
{
$intMainId = $arrRow[0] ;
$floOrder = $arrRow[1] ;
$intLevel = $arrRow[2] ;
}
mysql_free_result ( $resResult ) ;

if ( ! $intMainId ) return false ;

$intLevelLastestId = $this->get_level_lastest_id ( $intParentId ) ;

// get pre order
if ( $intLevelLastestId )
{
$floPreOrder = $this->get_level_lastest_order ( $intLevelLastestId );
// echo $floPreOrder ;exit;
}
else
{
$floPreOrder = $floOrder ;
}

// get next order
$strQuery = " SELECT `$this->strFiled_order`
FROM `$this->strMenuTable`
WHERE `$this->strFiled_mainid` = $intMainId AND `$this->strFiled_order` > $floPreOrder
ORDER BY `$this->strFiled_order` ASC LIMIT 0 , 1 " ;
$resResult = mysql_query ( &$strQuery , $this->resDbc ) ;
while ( $arrRow = mysql_fetch_row ( $resResult ) )
{
$floNextOrder = $arrRow[0] ;
}
mysql_free_result ( $resResult ) ;

if ( ! $floNextOrder )
{
$floNewOrder = floor ( $floPreOrder + 1 ) ;
}
else
{

$floNewOrder = number_format ( ( $floPreOrder + $floNextOrder ) / 2 , 14 ) ;
}

$intNewLevel = $intLevel + 1 ;
return array ( "mainid" => $intMainId , "order" => $floNewOrder , "level" => $intNewLevel ) ;
}

function update_tree ( $intMainId , $intParentId , $floOrder )
{
if ( !$intParentId ) return false ;

mysql_select_db ( $this->strDatabase , $this->resDbc ) ;

$strQuery = " SELECT `tree`
FROM `$this->strMenuTreeTable`
WHERE `mainid` = $intMainId AND BINARY ( `tree`) LIKE '%|$intParentId|'
ORDER BY `order` DESC LIMIT 0 , 1 " ;
$resResult = mysql_query ( &$strQuery , $this->resDbc ) ;
while ( $arrRow = mysql_fetch_row ( $resResult ) )
{
$strTree = $arrRow[0] ;
}
mysql_free_result ( $resResult ) ;

if ( ! $strTree )
{
$strQuery = " SELECT `$this->strFiled_parentid`
FROM `$this->strMenuTable`
WHERE `$this->strFiled_id` = $intParentId " ;
$resResult = mysql_query ( &$strQuery , $this->resDbc ) ;
while ( $arrRow = mysql_fetch_row ( $resResult ) )
{
$intPreParentId = $arrRow[0] ;
}
mysql_free_result ( $resResult ) ;

if ( ! $intPreParentId )
{
$strPreTree = '';
}
else
{
$strQuery = " SELECT `tree`
FROM `$this->strMenuTreeTable`
WHERE `mainid` = $intMainId AND BINARY ( `tree`) LIKE '%|$intPreParentId|'
ORDER BY `order` DESC LIMIT 0 , 1 " ;
$resResult = mysql_query ( &$strQuery , $this->resDbc ) ;
while ( $arrRow = mysql_fetch_row ( $resResult ) )
{
$strPreTree = $arrRow[0] ;
}
mysql_free_result ( $resResult ) ;
}

$strNewTree = $strPreTree . '|'. $intParentId . '|' ;
$strQuery = " INSERT INTO `$this->strMenuTreeTable`
VALUES ( $intMainId, '$strNewTree', $floOrder ) " ;
$resResult = mysql_query ( &$strQuery , $this->resDbc ) ;
@mysql_free_result ( $resResult ) ;
return true ;
}
else
{
$strQuery = " UPDATE `$this->strMenuTreeTable`
SET `order` = $floOrder
WHERE `mainid` = $intMainId AND `tree` = '$strTree' " ;
$resResult = mysql_query ( &$strQuery , $this->resDbc ) ;
@mysql_free_result ( $resResult ) ;
return true ;
}
}
}
}

/*
$pFreeRoad = new FreeRoad ( $resDbc , $arrDatabase["dbname"] , 'menus' , 'menu_tree' ) ;

$info = 'change here';

$intParentId = change here ;
$arrItems = $pFreeRoad->get_elements( $intParentId ) ;
$intMainId = $arrItems['mainid'] ;
$floOrder = $arrItems['order'] ;
$intLevel = $arrItems['level'] ;

$strQuery = " INSERT INTO `menus` VALUES ( '' , $intMainId , $intParentId , $floOrder , $intLevel, '$info' ) " ;
$resResult = mysql_query ( &$strQuery , $resDbc ) ;

$pFreeRoad->update_tree ( $intMainId , $intParentId , $floOrder ) ;

@mysql_close( $resDbc ) ;
*/
?>

<?php
include "freeroad.class.php";
$strQuery = " SELECT * FROM `menus` ORDER BY `mainid` ASC , `order` ASC ";
$resResult = mysql_query ( &$strQuery , $resDbc ) ;
while ( $arrRows = mysql_fetch_array ( $resResult ))
{
$intLevel = $arrRows["level"] ;
$strSpace = '' ;
for ( $i = 0 ; $i <= $intLevel ; $i++ )
{
$strSpace .= "　　";
}
if ( $i>1 )
{
$strSpace .= '--';
}
echo $strSpace . $arrRows["id"] . $arrRows["info"] ."<br>";
}

if ( $_GET["action"] == 'add' )
{

$pFreeRoad = new FreeRoad ( $resDbc , $arrDatabase["dbname"] , 'menus' , 'menu_tree' ) ;

$info = 'F1';

$intParentId = 1 ;
$arrItems = $pFreeRoad->get_elements( $intParentId ) ;
$intMainId = $arrItems['mainid'] ;
$floOrder = $arrItems['order'] ;
$intLevel = $arrItems['level'] ;

$strQuery = " INSERT INTO `menus` VALUES ( '' , $intMainId , $intParentId , $floOrder , $intLevel, '$info' ) " ;
$resResult = mysql_query ( &$strQuery , $resDbc ) ;

$pFreeRoad->update_tree ( $intMainId , $intParentId , $floOrder ) ;

@mysql_close( $resDbc ) ;

}
?>