Looking For Cheapest SMS Sending Service With API

<?php
// Using http://unirest.io/php
$response = Unirest\Request::post("https://twilio.p.mashape.com/{accountsid}/SMS/Messages.json",
  array(
  "Authorization" => "<required>",
  "X-Mashape-Key" => "<your mashape key>",
  "Content-Type" => "application/x-www-form-urlencoded",
  "Accept" => "text/plain"
  ),
  array(
  "Body" => "<required>",
  "From" => "<required>",
  "To" => "<required>"
  )
);