Send email using PHP/cURL + Mailgun

mailgun.php

<?php

// [TODO] Update below parameters
define('MAILGUN_KEY', 'XXX-XXX...XXX');
define('MAILGUN_URL', 'https://api.mailgun.net/v3/mg.domain.tld');
define('MAIL_FROM', '[email protected]');
define('MAIL_REPLY', '[email protected]');

function mailgun($to, $subject, $body, array $params = []) {
    $data = array_merge([
        'from' => MAIL_FROM,
        'to' => $to,
        'subject' => $subject,
        'html' => $body,
        'h:Reply-To' => MAIL_REPLY,
    ], $params);
    $ch = curl_init(MAILGUN_URL . '/messages');
    curl_setopt($ch, CURLOPT_HTTPAUTH, CURLAUTH_BASIC);
    curl_setopt($ch, CURLOPT_USERPWD, 'api:'.MAILGUN_KEY);
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
    curl_setopt($ch, CURLOPT_HEADER, false);
    curl_setopt($ch, CURLOPT_ENCODING, 'UTF-8');
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    $response = curl_exec($ch);
    curl_close($ch);
    return json_decode($response, true);
}