Call to undefined function curl_init() in

selamat siang pas ane pakai mysqli script berjalan lancar, perulangan pakai foreach, pas sama ane d rubah pakai mssql perulangan pakai while malah curl nya ga berfungsi kira2 apa ada yang pernah mengalami?

<?php

session_start();
include'koneksi.php';

$tanggal = date("Y-m-d");

$telepon=$_SESSION['tlp'] ;
$message=$_SESSION['msg'];
// Script Kirim SMS Api Zenziva
$userkey = "*****"; //userkey lihat di zenziva
$passkey = "*****"; // set passkey di zenziva

$sql 	=mssql_query( "SELECT OS_ID, OS_MESSAGE, OS_Receiver FROM OTHE_SMS WHERE OS_Receiver = '$telepon' or OS_MESSAGE = '$message'   ");
while($key = mssql_fetch_assoc($sql)){

$url = "https://reguler.zenziva.net/apps/smsapi.php";
$curlHandle = curl_init(); //// ini yg error
curl_setopt($curlHandle, CURLOPT_URL, $url);
curl_setopt($curlHandle, CURLOPT_POSTFIELDS, 'userkey='.$userkey.'&passkey='.$passkey.'&nohp='.$key['OS_Receiver'].'&pesan='.urlencode($message['OS_MESSAGE']));
curl_setopt($curlHandle, CURLOPT_HEADER, 0);
curl_setopt($curlHandle, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($curlHandle, CURLOPT_SSL_VERIFYHOST, 2);
curl_setopt($curlHandle, CURLOPT_SSL_VERIFYPEER, 0);
curl_setopt($curlHandle, CURLOPT_TIMEOUT,30);
curl_setopt($curlHandle, CURLOPT_POST, 1);
$results = curl_exec($curlHandle);
curl_close($curlHandle);



		$XMLdata = new SimpleXMLElement($results);
		$status = $XMLdata->message[0]->text;

		header("location: sms_otomatis.php");

	}

?>