如何在多维数组中遵循父子关系？

Question

我有一个经典数据库 table 用于像这样的多级类别（0 表示根）：

ID - Name - Father
1    News      0
2    Articles  0
3    Politics  1
4    Politics  2
5    World     3
6    World     4

我有这样的路径：/News/Articles/Politics，并且我在数组中有上述 table 数据。

我从路径上的 / 调用 explode() 开始，我尝试了一些方法，但在所有情况下都不好。

这是我试过的东西：

$cat_path_ary = explode($cfg['categories_separator'], $cat_path);
if (count($cat_path_ary) > 1) {
    $catname = array_pop($cat_path_ary);
    $catparent = array_pop($cat_path_ary);
    $cat_id = $this->getCatIDbyName($plugin, $catname, $catparent);
} else {
   $catname = $cat_path_ary[0];
   foreach($this->root_cats($plugin) as $categories) {
      if($categories['name'] == $catname ) {
       return $categories['cid'];
      }
   }
}

遍历路径值并确定最终值的最佳方法是什么ID？

从 /News/Articles/Politics 我希望 return 5.

Answer 1

我很少建议对数据库进行迭代调用，这种情况也不例外。因为您的结果集应该相对较小，所以您可以执行完整的 table 查询并处理多维数组以获得所需的输出。

迭代路径中的条目并对符合条件的行执行迭代检查（匹配 Name 和匹配 Father）。

由于每个内循环只能有一个符合条件的行，break 一旦找到它以获得最佳效率。 ...在这样做之前一定要更新 $id 和 $parent 变量。

已实施 "no qualifying rows" 检查，但它可能与您的项目相关，也可能不相关。您可以决定是否需要此安全网。

代码：(Demo)

$resultset = [                                                     // query just once, collect the full tree
    ["ID" => 1, "Name" => "News", "Father" => 0],
    ["ID" => 2, "Name" => "Articles", "Father" => 0],
    ["ID" => 3, "Name" => "Politics", "Father" => 1],
    ["ID" => 4, "Name" => "Politics", "Father" => 2],
    ["ID" => 5, "Name" => "World", "Father" => 3],
    ["ID" => 6, "Name" => "World", "Father" => 4]
];

$path = "/News/Politics/World";
// $path = "/Articles/The Funnies/Garfield";                        // a test case that fails
// News: parent = 0, id = 1                                         // \
// Politics: parent = 1, id = 3                                     //  > the intended logic
// World: parent = 3, id = 5                                        // /

$cfg['categories_separator'] = "/";
$breadcrumbs = explode($cfg['categories_separator'], trim($path, "/"));
// var_export($breadcrumbs);                                        // see what is generated

$parent = 0;                                                        // default value
foreach ($breadcrumbs as $crumb) {
    $id = false;                                                    // set invalid value for success check
    foreach ($resultset as $row) {
        if ($row["Name"] == $crumb && $parent == $row["Father"]) {  // qualifying match
            $id = $parent = $row["ID"];                             // dual declaration
            break;                                                  // break inner loop, progress to next $crumb        
        }
    }
    if (!$id) {                                                     // inner loop failed to find qualifying match
        echo "Uh-oh, Broken Breadcrumb Path -- $crumb not found in $path\n";
        break;                                                      // break outer loop, path is invalid
    }
    // echo "ID = $id for $crumb\n";                                // uncomment to see progress
}
echo "ID = $id for $crumb\n";                                       // echo the result

输出：

ID = 5 for World

如何在多维数组中遵循父子关系？

How to follow parent-child relationships in a multi-dimensional array?

php

tree

search

loops

categories