php - Interview question: Article list and category list (both two-dimensional), if the category corresponding to the article is taken out through a loop

Question

P.S.: They are all two-dimensional arrays (numeric index)

I also want to ask: Where is the inspection point? The context of the Lenovo interview was maybe a function test?

Answer 1

I guess it’s the array_column function.

# 数据准备
$articles = [
    ['id' => 1, 'name' => '文章1', 'category_id' => 3],
    ['id' => 2, 'name' => '文章2', 'category_id' => 5],
    ['id' => 3, 'name' => '文章3', 'category_id' => 6]
];
$categories = [
    ['id' => 1, 'name' => '分类1'],
    ['id' => 2, 'name' => '分类2'],
    ['id' => 3, 'name' => '分类3'],
    ['id' => 4, 'name' => '分类4'],
    ['id' => 5, 'name' => '分类5'],
    ['id' => 6, 'name' => '分类6']
];

$categories = array_column($categories, NULL, 'id');
# 经过上面这步之后，新的$categories值如下：
# [
#     '1' => ['id' => 1, 'name' => '分类1'],
#     '2' => ['id' => 2, 'name' => '分类2'],
#     '3' => ['id' => 3, 'name' => '分类3'],
#     '4' => ['id' => 4, 'name' => '分类4'],
#     '5' => ['id' => 5, 'name' => '分类5'],
#     '6' => ['id' => 6, 'name' => '分类6']
# ];
# array_column函数将一个二维矩阵型的数组中的列拆出来，输出一维数组。
# 这个函数有三个参数，第一个参数为源数组
# 第二个参数为取出来当键值的列名，比如这个例子中对$categories可以取'id'或者'name'，当然也可以用NULL，表示将整个值（此处为['id' => 1, 'name' => '分类1']之类）原封不动作为新的值
# 第三个参数为取出来当键名的列，可选。如果不给或者为NULL，则自动编号。
#
# 上面做的这个array_column操作，是让之后遍历文章时，可以通过里面的category_id列的值直接找到对应的$categories里面的值。

foreach($articles as &$article) {
    $cat_id = $article['category_id']; // 这步可以嵌入下面的代码，是为了看起来没那么多嵌套而已
    $article['category'] = $categories[$cat_id];
}

# 新的$articles：
# [
#     ['id' => 1, 'name' => '文章1', 'category_id' => 3, 'category' => ['id' => 3, 'name' => '分类3']],
#     ['id' => 2, 'name' => '文章2', 'category_id' => 5, 'category' => ['id' => 5, 'name' => '分类5']],
#     ['id' => 3, 'name' => '文章3', 'category_id' => 6, 'category' => ['id' => 6, 'name' => '分类6']]
# ];