php - 如何对数组项进行分类？

Question

我有一个查询，它在一页中获取所有问题和答案的评论(每个页面至少包含一个帖子(问题)，并且可能加上一个或多个帖子(答案))。现在我需要根据自己的问题或答案来分隔评论。

我的查询结果(获取所有评论)是这样的:

while ($results = $sth->fetch(PDO::FETCH_ASSOC)) {
    echo '<pre>';        
    print_r($results);
}

/* Output:
            Array
            (
                 [id] => 1
                 [post_id] => 1
                 [content] => Have you any tried so far? 
            )

            Array
            (
                 [id] => 2
                 [post_id] => 3
                 [content] => Great answer, upvote 
            )

            Array
            (
                 [id] => 3
                 [post_id] => 3
                 [content] => That semicolon is redundant in line 5. Pplease edit it
            )

            Array
            (
                 [id] => 4
                 [post_id] => 2
                 [content] => Won't work ...!
            )

            Array
            (
                 [id] => 5
                 [post_id] => 3
                 [content] => @alex You are right thanks, Edited.
            )

所以，正如您在输出中看到的，所有评论都是混合的。现在我需要对它们进行分类。像这样:

/* NewOutput:

            [1] => Array
     post_id ^     (
                        [0] => Array
                               (
                                   [id] => 1
                                   [content] => Have you any tried so far?
                               )
                   )

            [2] => Array
     post_id ^     (
                        [0] => Array
                               (
                                   [id] => 4
                                   [content] => Won't work ...!
                               )
                   )

            [3] => Array
     post_id ^     (
                        [0] => Array
                               (
                                   [id] => 2
                                   [content] => Great answer, upvote
                               )

                        [1] => Array
                               (
                                   [id] => 3
                                   [content] => That semicolon is redundant in line 5. Pplease edit it
                               )

                        [2] => Array
                               (
                                   [id] => 5
                                   [content] => @alex You are right thanks, Edited.
                               )
                   )

那么，现在我想知道，如何根据数组中特定键的值创建嵌套数组？和上面完全一样。

Answer 1

试试这个...

$output = array();
foreach($results as $r){
    $key = "post_".$r["post_id"];
    if(!array_key_exists($key, $output)){
        $output[$key] = array();
    }
    array_push($output[$key], array("id"=>$k["id"], "content"=>$k["content"]));
}
print_r($output);