$url = 'https://api.sendgrid.com/';
$user = 'MY_USER_ID';
$pass = 'MY_PASSWORD';

$fileName = 'week-19.pdf';
$filePath = dirname(__FILE__);

$params = array(
 'api_user' => $user,
 'api_key' => $pass,
 'to' =>'test@test.com',
 'subject' => 'Sendgrid test of file sends',
 'html' => '<p> the HTML </p>',
 'text' => 'the plain text',
 'from' => 'anna@test.com',
 'files['.$fileName.']' => '@'.$filePath.'/'.$fileName
);

print_r($params);

$request = $url.'api/mail.send.json';

// Generate curl request
$session = curl_init($request);

// Tell curl to use HTTP POST
curl_setopt ($session, CURLOPT_POST, true);

// Tell curl that this is the body of the POST
curl_setopt ($session, CURLOPT_POSTFIELDS, $params);

// Tell curl not to return headers, but do return the response
curl_setopt($session, CURLOPT_HEADER, false);
curl_setopt($session, CURLOPT_RETURNTRANSFER, true);

// obtain response
$response = curl_exec($session);
curl_close($session);

// print everything out
print_r($response);