How to send POST requests to the VK API

I have a VK bot that needs to send long messages. They do not fit in URI, if I try to send a GET request, API returns URI too long error. Sending requests with Content-Type: application/json and passing json as body doesn't work, neither is it possible to send a Content-Type: multipart/form-data request. Is it possible to send a POST request to VK API?

It is possible to send a POST request using Content-Type: application/x-www-form-urlencoded;charset=UTF-8. Also it's recommended to send access_token and v parameters in url and the rest in the body.

Example in JavaScript:

const TOKEN = '...'
const VERSION = '5.126'

fetch(`https://api.vk.com/method/messages.send?access_token=${TOKEN}&v=${VERSION}`, {
  method: 'POST',
  headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
  body: new URLSearchParams({
    random_id: Math.round(Math.random()*100000),
    peer_id: 185014513,
    message: 'Hello world'
  }).toString()
})
  .then((res) => res.json())
  .then(console.log)

In PHP:

const TOKEN = '...';
const VERSION = '5.126';

$query = http_build_query([
  'access_token' => TOKEN,
  'v' => VERSION,
]);
$body = http_build_query([
  'random_id' => mt_rand(0, 100000),
  'message' => 'Hello world',
  'peer_id' => 185014513,
]);
$url = "https://api.vk.com/method/messages.send?$query";

$curl = curl_init($url);
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_POSTFIELDS, $body);
curl_setopt($curl, CURLOPT_HTTPHEADER , [
  'Content-Type' => 'application/x-www-form-urlencoded; charset=UTF-8',
]);
$response = curl_exec($curl);
curl_close($curl);

$json = json_decode($response, true);

Note that you cannot send messages over 4096 characters long