GetAnnouncements

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'https://www.example.com/includes/api.php');
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS,
    http_build_query(
        array(
            'action' => 'GetAnnouncements',
            // See https://developers.whmcs.com/api/authentication
            'username' => 'IDENTIFIER_OR_ADMIN_USERNAME',
            'password' => 'SECRET_OR_HASHED_PASSWORD',
            'responsetype' => 'json',
        )
    )
);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$response = curl_exec($ch);
curl_close($ch);

$command = 'GetAnnouncements';
$postData = array(
);
$adminUsername = 'ADMIN_USERNAME'; // Optional for WHMCS 7.2 and later

$results = localAPI($command, $postData, $adminUsername);
print_r($results);

{
    "result": "success",
    "totalresults": "1",
    "startnumber": "0",
    "numreturned": "1",
    "announcements[announcement][0][id]": "1",
    "announcements[announcement][0][date]": "2016-02-24 21:27:04",
    "announcements[announcement][0][title]": "Thank you for choosing WHMCS!",
    "announcements[announcement][0][announcement]": "<p>Welcome to <a title=\"WHMCS\" href=\"https:\/\/whmcs.com\" target=\"_blank\">WHMCS<\/a>! You have made a great choice and we want to help you get up and running as quickly as possible.<\/p><p>This is a sample announcement. Announcements are a great way to keep your customers informed about news and special offers. You can edit or delete this announcement by logging into the admin area and navigating to <em>Support &gt; Announcements<\/em>.<\/p><p>If at any point you get stuck, our support team is available 24x7 to assist you. Simply visit <a title=\"www.whmcs.com\/support\" href=\"https:\/\/www.whmcs.com\/support\" target=\"_blank\">www.whmcs.com\/support<\/a> to request assistance.<\/p>",
    "announcements[announcement][0][published]": "1",
    "announcements[announcement][0][parentid]": "0",
    "announcements[announcement][0][language]": "",
    "announcements[announcement][0][created_at]": "0000-00-00 00:00:00",
    "announcements[announcement][0][updated_at]": "0000-00-00 00:00:00"
}