A class SmsSender is provided. To send messages using the API, simply include the class and use its sendMessage function:
<?php
require('SmsSender.class.php');
$username = 'username';
$password = 'password';
$sender = '+4542031337';
$recipient = '+4542001234';
$message = 'This is a Test Message.';
$smsSender = new SmsSender($username,$password);
$smsSender->sendMessage($sender,$recipient,$message);
?>
This source code is provided for free by Gigahost under the GPLv3 license.
These archives contain the SmsSender class and a small example, send_sms.php that illustrates how to use the class.
SmsSender.tar.gz, gzip-compressed tar archive.
SmsSender.zip, zip file.