sendsms-curl.php

<?php

$url = "https://gateway.standingtech.com/api/v4/sms/send";

$curl = curl_init($url);
curl_setopt($curl, CURLOPT_URL, $url);
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);

$headers = array(
   "Authorization: Bearer API_KEY",
   "Content-Type: application/json",
   "Accept: application/json",
);
curl_setopt($curl, CURLOPT_HTTPHEADER, $headers);

$data = <<<DATA
{"recipient":"9647xxxxxxxxx",
"sender_id":"SenderID",
"type":"plain",
"message":"Your OTP Code is: 123654"
}
DATA;

curl_setopt($curl, CURLOPT_POSTFIELDS, $data);

//for debug only!
curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, false);
curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);

$resp = curl_exec($curl);
curl_close($curl);
var_dump($resp);

?>