Qiniu\Storage\FormUploader::createFile PHP Method

    private static function createFile($filename, $mime)
    {
        // PHP 5.5 introduced a CurlFile object that deprecates the old @filename syntax
        // See: https://wiki.php.net/rfc/curl-file-upload
        if (function_exists('curl_file_create')) {
            return curl_file_create($filename, $mime);
        }
        // Use the old style if using an older version of PHP
        $value = "@{$filename}";
        if (!empty($mime)) {
            $value .= ';type=' . $mime;
        }
        return $value;
    }