gmail api send

mail

$url= "https://www.googleapis.com/upload/gmail/v1/users/me/messages/send";
$header = array('Content-Type: message/rfc822', "Authorization: Bearer $access_token");

        $from = "<$user_name> $user_email";
        $line = "rn";
        $raw = "Content-type: text/html; charset=UTF-8".$line;
        $raw .= "To: $to ".$line;
        $raw .= "from: $from".$line;
        $raw .= "Reply-To: $user_email".$line;
        $raw .= "subject: $subject".$line.$line;
        //$raw .= "Reply-To: $user_email".$line;
        $raw .= $message;

$curl = curl_init();
    curl_setopt($curl, CURLOPT_URL, $url);
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, 0);
    curl_setopt($curl, CURLOPT_HEADER, 0);

    if( $header !== 0 ){
    curl_setopt($curl, CURLOPT_HTTPHEADER, $header);
    }

    curl_setopt($curl, CURLOPT_POST, 1);

    if( $data !== 0 ){
    curl_setopt($curl, CURLOPT_POSTFIELDS, $data);
    }
    $response = curl_exec($curl);
    $json = json_decode($response, true);
    curl_close($curl);