How to send out multi emails using mailgun API in PHP - php

Question

I have tried to run the following code for sending multiple emails using mailgun API in PHP. But no email is sent using the code. My code is :
require 'vendor/autoload.php';
use Mailgun\Mailgun;
$mgClient = new Mailgun("my-api-key");
$domain = "sandboxfa3e9009746840be831c6edc9e9f1ee9.mailgun.org";
$result = $mgClient->sendMessage("$domain",
array('from' => 'Mailgun Sandbox - Test
<postmaster#sandboxfa3e9009746840be831c6edc9e9f1ee9.mailgun.org>',
'to' => 'email_1#gmail.com, email_2#gmail.com',
'subject' => 'Mailgun bulk-msg test for KB',
'text' => 'Your mail do not support HTML',
'html' => 'html-portion here...',
'recipient-variables' => '{"email_1#gmail.com": {"first":"Name-1",
"id":1}, "email_2#gmail.com": {"first":"Name-2", "id": 2}}')
);
var_dump($result);
?>
#===============================================
Have i do any mistake in the code to send multi email ? If you have any solution, please help.

Answer 1

I found this from their API. (Not as answer maybe. Just a reference)
require 'vendor/autoload.php';
use Mailgun\Mailgun;
$mg = Mailgun::create('key-example');
# $mg->messages()->send($domain, $params);
$mg->messages()->send('example.com', [
'from' => 'bob#example.com',
'to' => 'sally#example.com',
'subject' => 'The PHP SDK is awesome!',
'text' => 'It is so simple to send a message.'
]);
Source

Answer 2

Aside from what Abdulla pointed out I see that you're writing "$domain" as the literal domain parameter. If you write it with quotation-marks, then it will be interpreted as a string, and not the variable itself.
Change the following and it should work:
$result = $mgClient->sendMessage("$domain",
[...]
to
$result = $mgClient->sendMessage($domain,
[...]