PHP Infinitus Classification Skillfully Uses Reference Spanning Tree_PHP Tutorial

First look at the code implementation

function generateTree($items){
    $tree = array();
    foreach($items as $item){
        if(isset($items[$item['pid']])){
            $items[$item['pid']]['son'][] = &$items[$item['id']];
        }else{
            $tree[] = &$items[$item['id']];
        }
    }
    return $tree;
}
$items = array(
    1 => array('id' => 1, 'pid' => 0, 'name' => '安徽省'),
    2 => array('id' => 2, 'pid' => 0, 'name' => '浙江省'),
    3 => array('id' => 3, 'pid' => 1, 'name' => '合肥市'),
    4 => array('id' => 4, 'pid' => 3, 'name' => '长丰县'),
    5 => array('id' => 5, 'pid' => 1, 'name' => '安庆市'),
);
print_r(generateTree($items));

Output results

Array
(
    [0] => Array
        (
            [id] => 1
            [pid] => 0
            [name] => 安徽省
            [son] => Array
                (
                    [0] => Array
                        (
                            [id] => 3
                            [pid] => 1
                            [name] => 合肥市
                            [son] => Array
                                (
                                    [0] => Array
                                        (
                                            [id] => 4
                                            [pid] => 3
                                            [name] => 长丰县
                                        )
 
                                )
 
                        )
 
                    [1] => Array
                        (
                            [id] => 5
                            [pid] => 1
                            [name] => 安庆市
                        )
 
                )
 
        )
 
    [1] => Array
        (
            [id] => 2
            [pid] => 0
            [name] => 浙江省
        )

)

It's really great, the code is concise and refined, no recursion is needed, and the execution speed is fast. I saw this on a website by chance. I thought it was very useful so I saved it and shared it with everyone.

---------------------------------------- The box below was proposed by the previous blogger Question, I don’t understand what it means. Sorry! ----------------------------------------

The above spanning tree method can also be reduced to 5 lines:

上面生成树方法还可以精简到5行：

function generateTree($items){
    foreach($items as $item)
        $items[$item['pid']]['son'][$item['id']] = &$items[$item['id']];
    return isset($items[0]['son']) ? $items[0]['son'] : array();
}

上面这种无限极分类数据树形结构化的方法值得借鉴。但是我觉得这段代码实际用途并不明显啊，你想取出格式化的树形数据还是要递归啊：

/**
 * 如何取数据格式化的树形数据
 */
$tree = generateTree($items);
function getTreeData($tree){
    foreach($tree as $t){
        echo $t['name'].'<br>';
        if(isset($t['son'])){
            getTreeData($t['son']);
        }
    }
}
getTreeData($tree);

The above tree-structured method of Infinitus classification data is worth learning from. But I think the actual use of this code is not obvious. If you want to take out the formatted tree data, you still have to recurse:

I don’t understand why he still needs to take it out recursively. Wouldn’t it be good to output the return value of generateTree() as json to the front end?

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First look at the code implementation function generateTree($items){ $tree = array(); foreach($items as $ item){ if(isset($items[$item['pid']])){ $items[$item['pid']]['son'][] = $items[$item['id'] ]...