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：
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$arr = array(
array("id" => 1 , "pid" => 0 , 'cat' => '栏目一'),
array("id" => 2 , "pid" => 0 , 'cat' => '栏目二'),
array("id" => 3 , "pid" => 1 , 'cat' => '栏目三'),
array("id" => 4 , "pid" => 2 , 'cat' => '栏目四'),
array("id" => 5 , "pid" => 1 , 'cat' => '栏目五'),
array("id" => 6 , "pid" => 5 , 'cat' => '栏目六'),
array("id" => 7 , "pid" => 5 , 'cat' => '栏目七'),
array("id" => 8 , "pid" => 6 , 'cat' => '栏目八'),
array("id" => 9 , "pid" => 1 , 'cat' => '栏目九'),
array("id" => 10 , "pid" => 0 , 'cat' => '栏目十'),
array("id" => 11 , "pid" => 10 , 'cat' => '栏目十一'),
array("id" => 12 , "pid" => 11 , 'cat' => '栏目十二'),
array("id" => 13 , "pid" => 2 , 'cat' => '栏目十三'),
array("id" => 14, "pid" => 13 , 'cat' => '栏目十四')
);
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不多说，直接上处理代码：
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//生成无限极分类树
function make_tree($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]; //*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 $tree;
}
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测试运行：
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$cat = make_tree($arr);
print_r($cat);
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运行结果：
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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
)
)
)
)
)
)
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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
希望本文所述对大家PHP程序设计有所帮助。
原文链接：http://blog.csdn.net/zhang197093/article/details/49962541