如何在PHP中将此MPTT数组转换为树结构?
我在数据库中有分层数据,按格式存储。我在一个查询中提取数据,该查询类似于“按如何在PHP中将此MPTT数组转换为树结构?,php,arrays,tree,mptt,Php,Arrays,Tree,Mptt,我在数据库中有分层数据,按格式存储。我在一个查询中提取数据,该查询类似于“按左;”从表顺序中选择ID、左、右、名称等”。我试图将DB提供的平面数组中的数据转换为树结构,然后使用PHP的JSON_encode函数将其输出为JSON 不过,我很难让我的树结构代码在第一级之外工作。下面是一个最低测试用例: 正如您所看到的,尽管projectListToTree函数中的输出似乎表明它应该在那里,但“孙子”正在丢失。好像我扔给它的任何树结构都会把第二层以下的东西掉下来。对可能发生的事情有什么见解吗 谢谢
左
;”从表顺序中选择ID、左
、右
、名称等”。我试图将DB提供的平面数组中的数据转换为树结构,然后使用PHP的JSON_encode函数将其输出为JSON
不过,我很难让我的树结构代码在第一级之外工作。下面是一个最低测试用例:
正如您所看到的,尽管projectListToTree函数中的输出似乎表明它应该在那里,但“孙子”正在丢失。好像我扔给它的任何树结构都会把第二层以下的东西掉下来。对可能发生的事情有什么见解吗
谢谢 问题在于分配数组不会复制引用,而是复制数组。这意味着,您在“父”节点的“子”中拥有的“第二个子”数组不是添加“孙子”到的同一数组,而是它的副本 要解决此问题,必须显式使用引用分配,而不是复制:
功能项目列表目录($projects){
$stack=Array();
对于($x=0;$x0&&$stack[count($stack)-1]['Right']<$project['Right']{
数组_pop($stack);
}
如果(计数($stack)>0){
$stack[count($stack)-1]['Children'][]=&$project;
echo“将“$project['Name']”添加到“$stack[count($stack)-1]['Name']”中,总共
.count($stack[count($stack)-1]['Children'])“Children\n”;
回音“\n”;
}否则{
回显“无父项\n”;
}
回显“堆栈计数:”.count($stack)。“\n”;
$stack[]=&$project;
}
echo“堆栈中的左侧:”.count($stack)。“\n”;
返回$stack[0];
}
请注意,在三个位置添加了一个符号AND
由于这个问题,在php中使用嵌套数组和赋值运算符时必须非常小心
这还意味着,在嵌套阵列中使用大量数据时,处理器使用率和内存占用率会非常高。例如,在上面的示例中,当projectListToTree()返回时,完整的数组树被复制到局部变量$tree中,并且(因为php垃圾回收器吸吮)在内存中存在两次。您是否在调用array_pop()时放入了echo语句?没有经过测试就阅读了这篇文章,我想你是在把这张唱片从堆栈中弹出并扔掉。谢谢!我想我仍然习惯于将数组视为对象并通过引用进行赋值的语言。除了关于数组推送($stack,&$project)行的警告(通过引用传递的调用时间已被弃用)之外,这一点工作得非常好,我将其更改为$stack[]=&$project;,从而对其进行了更正;。我更改了答案中的密码以避开警告。
<pre><?php
function projectListToTree($projects) {
$stack = Array();
for($x =0; $x < count($projects); $x++) {
$project = $projects[$x];
$project['Children'] = Array();
while(count($stack) > 0 && $stack[count($stack) - 1]['Right'] < $project['Right']) {
array_pop($stack);
}
if(count($stack) > 0) {
$stack[count($stack) - 1]['Children'][] = $project;
echo "Adding " . $project['Name'] . " to " . $stack[count($stack) - 1]['Name'] . " for a total of "
. count($stack[count($stack) - 1]['Children']) . " kids\n";
} else {
echo "No parent\n";
}
echo "stack count: " . count($stack) . "\n";
array_push($stack, $project);
}
echo "Left in stack: " . count($stack) . "\n";
return $stack[0];
}
/*
This is basically what comes from the DB.
Should be:
Parent
First Child
Second Child
Grand Child
*/
$projects = Array(
Array(
"ID" => "2",
"Left" => "2",
"Right" => "9",
"ParentID" => "1",
"Name" => "Parent"
),
Array(
"ID" => "3",
"Left" => "3",
"Right" => "4",
"ParentID" => "2",
"Name" => "First Child"
),
Array(
"ID" => "4",
"Left" => "5",
"Right" => "8",
"ParentID" => "2",
"Name" => "Second Child"
),
Array(
"ID" => "5",
"Left" => "6",
"Right" => "7",
"ParentID" => "4",
"Name" => "Grand Child"
)
);
$tree = projectListToTree($projects);
echo "-----\n\n\n\n";
var_dump($tree);
?></pre>
No parent
stack count: 0
Adding First Child to Parent for a total of 1 kids
stack count: 1
Adding Second Child to Parent for a total of 2 kids
stack count: 1
Adding Grand Child to Second Child for a total of 1 kids
stack count: 2
Left in stack: 3
-----
array(6) {
["ID"]=>
string(1) "2"
["Left"]=>
string(1) "2"
["Right"]=>
string(1) "9"
["ParentID"]=>
string(1) "1"
["Name"]=>
string(6) "Parent"
["Children"]=>
array(2) {
[0]=>
array(6) {
["ID"]=>
string(1) "3"
["Left"]=>
string(1) "3"
["Right"]=>
string(1) "4"
["ParentID"]=>
string(1) "2"
["Name"]=>
string(11) "First Child"
["Children"]=>
array(0) {
}
}
[1]=>
array(6) {
["ID"]=>
string(1) "4"
["Left"]=>
string(1) "5"
["Right"]=>
string(1) "8"
["ParentID"]=>
string(1) "2"
["Name"]=>
string(12) "Second Child"
["Children"]=>
array(0) {
}
}
}
}
function projectListToTree($projects) {
$stack = Array();
for($x =0; $x < count($projects); $x++) {
$project = &$projects[$x];
$project['Children'] = array();
while(count($stack) > 0 && $stack[count($stack) - 1]['Right'] < $project['Right']) {
array_pop($stack);
}
if(count($stack) > 0) {
$stack[count($stack) - 1]['Children'][] = &$project;
echo "Adding " . $project['Name'] . " to " . $stack[count($stack) - 1]['Name'] . " for a total of "
. count($stack[count($stack) - 1]['Children']) . " kids\n";
echo "\n";
} else {
echo "No parent\n";
}
echo "stack count: " . count($stack) . "\n";
$stack[] = &$project;
}
echo "Left in stack: " . count($stack) . "\n";
return $stack[0];
}