How to attach data from one array to another in php - php

Question

I am building a [post, comments] project where post details are stored in posts table and comment details are stored in comments table. The project is generated in Laravel(Php). Here is the piece of code.
//get data from Post table
$posts = $this->postsRepo->getAllPosts();
//get data from comments table
$comments = $this->commentRepo->getAllComments();
print_r($posts);
print_r($comments);
The result of post table
Array
(
[0] => stdClass Object
(
[id] => 1
[post_text] => This is a test post
)
)
[1] => stdClass Object
(
[id] => 2
[post_text] => This is another test
)
)
The result of comments table
Array
(
[0] => stdClass Object
(
[id] => 1
[post_id] => 1
[comments_text] => This is a test comment 1
)
[1] => stdClass Object
(
[id] => 2
[post_id] => 1
[comments_text] => This is a test comment 2
)
)
Now I want result like
Array
(
[0] => stdClass Object
(
[id] => 1
[post_title] => This is a test post
[comments] => Array
(
[0] => stdClass Object
(
[id] => 1
[post_id] => 1
[comment_text] => This is a test comment 1
)
[1] => stdClass Object
(
[id] => 2
[post_id] => 1
[comment_text] => This is a test comment 2
)
)
)
)
[1] => stdClass Object
(
[id] => 2
[post_title] => This is another test
[comments] => Array()
)
)
I've used following technique, and it is working
foreach ($posts as $postIndex => $post) {
foreach ($comments as $commentIndex => $comment) {
if($post->id == $comment->post_id) {
$posts[$postIndex]->comments[] = $comment;
}
}
}
There's another way like running comments inside post for loop. I'll send the post_id to comments table. But this technique will be slow, as data increases
Could anybody please suggest a better technology to solve this issue?
Also, I used Repository design pattern for getting posts & comments

Answer 1

There are a couple of ways of doing this, depending on the version of PHP your using (although 1 will always work). The main principle is to index one of the arrays by the ID so that instead of looping over both arrays, you can use an index to set the values. As each post can have multiple comments, it seemed easier to index the posts by the ID and loop over the comments adding them into the correct post...
$posts = [
(object)[
"id" => 1,
"post_text" => "This is a test post"
],
(object)[
"id" => 2,
"post_text" => "This is another test"
]
];
$comments = [(object)
[
"id" => 1,
"post_id" => 1,
"comments_text" => "This is a test comment 1"
],
(object)
[
"id" => 2,
"post_id" => 1,
"comments_text" => "This is a test comment 2"
]
];
$postIndex = array_column($posts, null, "id");
//$postIndex = array_reduce($posts, function ($result, $post) { // PHP pre 7
// $result[$post->id] = $post;
// return $result;
//}, array());
foreach ( $comments as $comment ) {
$postIndex[ $comment->post_id ]->comments[] = $comment;
}
echo "<pre>";
print_r($postIndex);
Outputs...
Array
(
[1] => stdClass Object
(
[id] => 1
[post_text] => This is a test post
[comments] => Array
(
[0] => stdClass Object
(
[id] => 1
[post_id] => 1
[comments_text] => This is a test comment 1
)
[1] => stdClass Object
(
[id] => 2
[post_id] => 1
[comments_text] => This is a test comment 2
)
)
)
[2] => stdClass Object
(
[id] => 2
[post_text] => This is another test
)
)
The only difference is that from PHP 7.0, you can use array_column() with an array of objects. Prior to that you had to manually do the conversion.

Answer 2

You better use eloquent relationships...
but to answer your question for current case, if you need to accomplish this in php way.
// for all the post of the posts array
foreach ($posts as $key => $value) {
// get comments which only belongs to the post
$post_comments = [];
foreach ($comments as $comment) {
if ($comment['post_id'] == $value['id']) {
array_push($post_comments, $comment);
}
}
// add a new attribute (comments) to each post
// set created comments array of the post
$post[$key]['comments'] = $post_comments;
}

Answer 3

If you loop posts then you can use array_intersect and array_intersect_key.
This means you only loop one array once but use array functions to get the correct comments.
This means the arrays have to be arrays and not objects.
Foreach($posts as $key => $post){
$matches = array_intersect(array_column($comments, "post_id"), [$post["id"]]);
$new[$key][] = $post;
$new[$key]["comments"][] = array_intersect_key($comments, $matches);
}
Var_dump($new);
https://3v4l.org/eq20D