本文实例讲述了PHP实现无限极分类生成分类树的方法。分享给大家供大家参考，具体如下：

现在的分类数据库设计基本都是：每一个分类有一个id主键字段，一个pid指向父类的id，这样便可实现无限级分类，取出的数据就是如下的格式：

$arr = array(

array("id" => 1 , "pid" => 0 , 'cat' => '栏目一'),

array("id" => 2 , "pid" => 0 , 'cat' => '栏目二'),

array("id" => 3 , "pid" => 1 , 'cat' => '栏目三'),

array("id" => 4 , "pid" => 2 , 'cat' => '栏目四'),

array("id" => 5 , "pid" => 1 , 'cat' => '栏目五'),

array("id" => 6 , "pid" => 5 , 'cat' => '栏目六'),

array("id" => 7 , "pid" => 5 , 'cat' => '栏目七'),

array("id" => 8 , "pid" => 6 , 'cat' => '栏目八'),

array("id" => 9 , "pid" => 1 , 'cat' => '栏目九'),

array("id" => 10 , "pid" => 0 , 'cat' => '栏目十'),

array("id" => 11 , "pid" => 10 , 'cat' => '栏目十一'),

array("id" => 12 , "pid" => 11 , 'cat' => '栏目十二'),

array("id" => 13 , "pid" => 2 , 'cat' => '栏目十三'),

array("id" => 14, "pid" => 13 , 'cat' => '栏目十四')

);

不多说，直接上处理代码：

//生成无限极分类树

function make_tree($arr){

$refer = array();

$tree = array();

foreach($arr as $k => $v){

$refer[$v['id']] = & $arr[$k]; //创建主键的数组引用

}

foreach($arr as $k => $v){

$pid = $v['pid']; //获取当前分类的父级id

if($pid == 0){

$tree[] = & $arr[$k]; //顶级栏目

}else{

if(isset($refer[$pid])){

$refer[$pid]['subcat'][] = & $arr[$k]; //如果存在父级栏目，则添加进父级栏目的子栏目数组中

}

}

}

return $tree;

}

测试运行：

$cat = make_tree($arr);

print_r($cat);

运行结果：

Array

(

[0] => Array

(

[id] => 1

[pid] => 0

[cat] => 栏目一

[subcat] => Array

(

[0] => Array

(

[id] => 3

[pid] => 1

[cat] => 栏目三

)

[1] => Array

(

[id] => 5

[pid] => 1

[cat] => 栏目五

[subcat] => Array

(

[0] => Array

(

[id] => 6

[pid] => 5

[cat] => 栏目六

[subcat] => Array

(

[0] => Array

(

[id] => 8

[pid] => 6

[cat] => 栏目八

)

)

)

[1] => Array

(

[id] => 7

[pid] => 5

[cat] => 栏目七

)

)

)

[2] => Array

(

[id] => 9

[pid] => 1

[cat] => 栏目九

)

)

)

[1] => Array

(

[id] => 2

[pid] => 0

[cat] => 栏目二

[subcat] => Array

(

[0] => Array

(

[id] => 4

[pid] => 2

[cat] => 栏目四

)

[1] => Array

(

[id] => 13

[pid] => 2

[cat] => 栏目十三

[subcat] => Array

(

[0] => Array

(

[id] => 14

[pid] => 13

[cat] => 栏目十四

)

)

)

)

)

[2] => Array

(

[id] => 10

[pid] => 0

[cat] => 栏目十

[subcat] => Array

(

[0] => Array

(

[id] => 11

[pid] => 10

[cat] => 栏目十一

[subcat] => Array

(

[0] => Array

(

[id] => 12

[pid] => 11

[cat] => 栏目十二

)

)

)

)

)

)

如果大家需要这样的组装格式，或者需要该格式方便后续的处理，可以尝试此方法

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