v3 "Hello World" for email, using SendGrid with PHP.

v3-hello-email.php

// using SendGrid's PHP Library
// https://github.com/sendgrid/sendgrid-php
<?php
// If you are using Composer
require 'vendor/autoload.php';

// If you are not using Composer (recommended)
// require("path/to/sendgrid-php/sendgrid-php.php");

$from = new SendGrid\Email("Example User", "test@example.com");
$subject = "Sending with SendGrid is Fun";
$to = new SendGrid\Email("Example User", "test@example.com");
$content = new SendGrid\Content("text/plain", "and easy to do anywhere, even with PHP");
$mail = new SendGrid\Mail($from, $subject, $to, $content);

$apiKey = getenv('SENDGRID_API_KEY');
$sg = new \SendGrid($apiKey);

$response = $sg->client->mail()->send()->post($mail);
echo $response->statusCode();
echo $response->headers();
echo $response->body();