Send a JSON message with Ably.com using JWT Authentication in PHP without using the official Ably PHP SDK.

ably-jwt-authentication-send-json.php

<?php

// $ composer require lcobucci/jwt

require __DIR__ . '/vendor/autoload.php';

use Lcobucci\JWT\Configuration;
use Lcobucci\JWT\Signer\Key\InMemory;
use Lcobucci\JWT\Signer\Hmac\Sha256;

$ably_publish_key = <YOUR PUBLISH KEY HERE>

list($api_key, $api_secret) = explode(":", $ably_publish_key);
$secret = base64_encode($api_secret);

$config = Configuration::forSymmetricSigner(new Sha256(), InMemory::base64Encoded($secret));
assert($config instanceof Configuration);

$now = new DateTimeImmutable();
$token = $config->builder(\Lcobucci\JWT\Encoding\ChainedFormatter::withUnixTimestampDates()) // withUnixTimestampDates removes microseconds 
                ->withHeader('kid', $api_key)
                ->issuedAt($now)
                ->expiresAt($now->modify('+5 minutes'))
                ->withClaim('x-ably-capability', "{\"*\":[\"*\"]}")
                ->getToken($config->signer(), $config->signingKey());

$params = http_build_query(["data"=> json_encode(["message"=>"Hello World"])]);

$headers[] = "Authorization: Bearer ".$token->toString();

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://rest.ably.io/channels/<YOUR CHANNEL>/publish");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $params);
$output = curl_exec($ch);
curl_close($ch);

// inspect the contents of $output to see if it worked!