$from = '*****@*****.**';
$recipients = '*****@*****.**';
$subject = 'this mail is sent via PHP SDK';
$aTTNAME = NULL;
$attachmentid = NULL;
$bcc = NULL;
$clicktrack = NULL;
$footer = NULL;
$fromname = 'SDK Sender Name ';
$opentrack = NULL;
$replytoid = NULL;
$tags = NULL;
$template = NULL;
$xAPIHEADER = NULL;
try {
    $response = $email->sendRest($apiKey, $content, $from, $recipients, $subject, $aTTNAME, $attachmentid, $bcc, $clicktrack, $footer, $fromname, $opentrack, $replytoid, $tags, $template, $xAPIHEADER);
    /**
    //example output
    var_dump($response);
    object(stdClass)#5 (3) {
      ["message"]=>
      string(7) "SUCCESS"
      ["errorcode"]=>
      string(1) "0"
      ["errormessage"]=>
      string(0) ""
    }
    */
    //var_dump($response);
    if (empty($response->errorcode)) {
        print "Email sent successfully.\n";