<?php

$sendgrid = new SendGrid("YOUR_SENDGRID_API_KEY");
$email    = new SendGrid\\Email();

$email->addTo("[email protected]")
      ->setFrom("[email protected]")
      ->setSubject("Subject Text")
      ->setText("This is a sample basic text email using ");
      
$attachment = '/path/to/your/file.pdf';
$content    = file_get_contents($attachment);
$content    = chunk_split(base64_encode($content));

$attachment = new Attachment();
$attachment->setContent($content);
$attachment->setType("application/pdf");
$attachment->setFilename("RenamedFile.pdf");
$attachment->setDisposition("attachment");
$email->addAttachment($attachment);

$sendgrid->send($email);