php - 递归无限分类，帮忙看看代码哪里有问题？
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问题描述
问 题
public $cats = array();
public function category($fid=0, $level=1, $cats) {
$sql = "select * from article_cat where cat_fid =:id";
try {
$stmt = $this->db->prepare($sql);
$stmt -> bindParam(":id", $fid, PDO::PARAM_INT);
$stmt -> execute();
$results = $stmt->fetchAll(PDO::FETCH_ASSOC);
foreach ($results as $v) {
array_push($this->cats, array($v['cat_name'], $level));
$this-> category($v['cat_id'], $level+1, $this->cats);
}
return $this->cats;
} catch(Exception $e) {
die($e->getMessage());
}
}会正确输出所有的分类值
array(6){
[
0
]=>array(2){
[
0
]=>string(8)"3G咨询"[
1
]=>int(1)
}[
1
]=>array(2){
[
0
]=>string(12)"系统分类"[
1
]=>int(1)
}[
2
]=>array(2){
[
0
]=>string(18)"网店帮助分类"[
1
]=>int(2)
}[
3
]=>array(2){
[
0
]=>string(12)"新手上路"[
1
]=>int(3)
}[
4
]=>array(2){
[
0
]=>string(12)"手机常识"[
1
]=>int(3)
}[
5
]=>array(2){
[
0
]=>string(12)"网店信息"[
1
]=>int(2)
}}
但是如果把代码稍加修改,把cats变量由类属性改成类方法里的一个变量参数（把public $cats = array(); 删除 ），
public function category($fid=0, $level=1, $cats = array()) {
$sql = "select * from article_cat where cat_fid =:id";
try {
$stmt = $this->db->prepare($sql);
$stmt -> bindParam(":id", $fid, PDO::PARAM_INT);
$stmt -> execute();
$results = $stmt->fetchAll(PDO::FETCH_ASSOC);
foreach ($results as $v) {
array_push($cats, array($v['cat_name'], $level));
$this-> category($v['cat_id'], $level+1, $cats);
}
return $cats;
} catch(Exception $e) {
die($e->getMessage());
}
}输出的数据少了，只输出了顶级分类
array(2){
[
0
]=>array(2){
[
0
]=>string(8)"3G咨询"[
1
]=>int(1)
}[
1
]=>array(2){
[
0
]=>string(12)"系统分类"[
1
]=>int(1)
}}
为什么？无法理解，问题出在哪里？
解决方案
先解决下楼主的的问题
楼主的第二段代码核心在于数组变量的引用，由于楼主的代码
public function category($fid = 0, $level = 1,$cats = array())
//$cats由于不是引用变量，所以每次递归，$cats都是临时生成的，所以到最后只有几个值。
//而第一段代码中楼主使用的是类变量保存递归结果，$this->cats在整个类中都是有效的。
//楼主改为一下代码即可
public function category($fid = 0, $level = 1,&$cats = array())输出结果
Array
(
[0] => Array
(
[0] => 顶级分类1
[1] => 1
)
[1] => Array
(
[0] => 1-子级1
[1] => 2
)
[2] => Array
(
[0] => 4-子级1
[1] => 3
)
[3] => Array
(
[0] => 4-子级2
[1] => 3
)
[4] => Array
(
[0] => 1-子级2
[1] => 2
)
[5] => Array
(
[0] => 顶级分类2
[1] => 1
)
[6] => Array
(
[0] => 2-子级1
[1] => 2
)
[7] => Array
(
[0] => 2-子级2
[1] => 2
)
[8] => Array
(
[0] => 顶级分类3
[1] => 1
)
)
我的解决方式
代码
<?php
$pdo = new PDO("mysql:host=localhost;dbname=test", "root", "root");
function getCategories(PDO $pdo, $pid = 0)
{
$sql = 'SELECT * FROM `category` WHERE pid=:pid';
$stmt = $pdo->prepare($sql);
$stmt->bindParam(':pid', $pid, PDO::PARAM_INT);
$stmt->execute();
$data = $stmt->fetchAll(PDO::FETCH_ASSOC);
foreach ($data as &$row) {
$row['subs'] = getCategories($pdo, $row['id']);
}
return $data;
}
$a = getCategories($pdo);
print_r($a);数据库
输出结果
Array
(
[0] => Array
(
[id] => 1
[name] => 顶级分类1
[pid] => 0
[subs] => Array
(
[0] => Array
(
[id] => 4
[name] => 1-子级1
[pid] => 1
[subs] => Array
(
[0] => Array
(
[id] => 8
[name] => 4-子级1
[pid] => 4
[subs] => Array
(
)
)
[1] => Array
(
[id] => 9
[name] => 4-子级2
[pid] => 4
[subs] => Array
(
)
)
)
)
[1] => Array
(
[id] => 5
[name] => 1-子级2
[pid] => 1
[subs] => Array
(
)
)
)
)
[1] => Array
(
[id] => 2
[name] => 顶级分类2
[pid] => 0
[subs] => Array
(
[0] => Array
(
[id] => 6
[name] => 2-子级1
[pid] => 2
[subs] => Array
(
)
)
[1] => Array
(
[id] => 7
[name] => 2-子级2
[pid] => 2
[subs] => Array
(
)
)
)
)
[2] => Array
(
[id] => 3
[name] => 顶级分类3
[pid] => 0
[subs] => Array
(
)
)
)这篇关于php - 递归无限分类，帮忙看看代码哪里有问题？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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