Документация по HTTP API для разработчика

<?php
$message = array(
    "username" => "123456789",
    "password" => md5("password"),
    "phone" => "375291310043",
    "text" => "Hello, World!"
);
 
$messageQuery = http_build_query($message); // returns username=123456789&password=1fa...
 
$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, 'https://api.csms.by/simple/send');
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_POSTFIELDS, $messageQuery;
 
$result = @json_decode(curl_exec($curl), true);
 
if ($result && isset($result['id'])) {
    echo "Message has been sent. MessageID=" . $result['id'];
} elseif ($result && isset($result['error'])) {
    echo "Error occurred while sending message. ErrorID=" . $result['error'];
} else {
    echo "Service error";
}