How to fetch API and merge arrays in PHP Guzzle - php

Question

I use PHP Guzzle to fetch API and want to merge JSON arrays.
The API URL is https://example.com/api/v2/content/?categories=1234,4321,1324,4231
The parameter categories is a single ID or an array of different IDs. Here is the JSON data.
{
"data":
{
"1234":[
{"title":"Title 1 here", "description":"Content 1 here"},
{"title":"Title 2 here", "description":"Content 2 here"},
...
],
"4321":[
{"title":"Title 1 here", "description":"Content 1 here"},
{"title":"Title 2 here", "description":"Content 2 here"},
...
],
...
},
"message":"OK",
"code":0
}
Here is the PHP code. It works for the request to a single ID, but not different IDs.
<?php
require "vendor/autoload.php";
use Symfony\Component\DomCrawler\Crawler;
use GuzzleHttp\Client;
if (isset($_GET["c"]) && is_numeric($_GET["c"])) {
$category = $_GET["c"];
}
// DIFFERENT IDs
$url = "https://example.com/api/v2/content/?categories=1234,4321,1324,4231";
// SINGLE ID
$url = "https://example.com/api/v2/content/?categories=$category";
$client = new Client();
$response = $client->request("GET", $url);
$html = $response->getBody();
$decode = json_decode($html);
// $category works for a single ID but not multiple IDs
foreach ($decode->data->$category as $data) {
$title = $data->title;
$description = $data->description;
$result = array(
"title" => $title,
"description" => $description,
"category" => $category
);
$dataList[] = $result;
}
echo json_encode($dataList);
?>
Please let me know your recommendation to fetch API and merge arrays. The JSON result look like.
{
"data":
[
{"title":"Title 1 here", "description":"Content 1 here", "category":"1234"},
{"title":"Title 2 here", "description":"Content 2 here", "category":"4321"},
...
],
"page":1,
"message":"OK",
"code":0
}
Also, I'd like to limit results by adding a $_GET['page'].
In general, the above JSON result is what I expect. Please share your code or idea to get the best result. Thanks much for your anwser!. P/s: I'm not knowledgeble about coding, a web builder with low-code :(