<?php
// If you are using Composer
require "<MY_PATH>/vendor/autoload.php";

$from = new SendGrid\Email(null, "<MY_FROM>@<EMAIL>");
$subject = "Hello World from the SendGrid PHP Library!";
$to = new SendGrid\Email(null, "<MY_TO>@<EMAIL>");
$content = new SendGrid\Content("text/plain", "Hello, Email!");
$mail = new SendGrid\Mail($from, $subject, $to, $content);

$sg = new \SendGrid("<MY_API_KEY>");

$response = $sg->client->mail()->send()->post($mail);
echo $response->statusCode() . PHP_EOL;
echo $response->body() . PHP_EOL;
echo implode(', ', $response->headers()) . PHP_EOL;