public function b2_upload_file($upload_url, $auth_token, $file_path)
        {
            $call_url   = $upload_url; // Upload URL, obtained from the b2_get_upload_url call
            $auth_token = $auth_token; // Obtained from the b2_authorize_account call
            $file_path  = $file_path; // The path to the file you wish to upload

            $handle = fopen($file_path, 'r');
            $read_file = fread($handle, filesize($file_path));

            $file_name = basename($file_path);
            $file_type = mime_content_type($file_path);
            $file_hash = sha1_file($file_path);

            // Add headers
            $headers = array(
                "Authorization: {$auth_token}",
                "X-Bz-File-Name: {$file_name}",
                "Content-Type: {$file_type}",
                "X-Bz-Content-Sha1: {$file_hash}"
            );

            $result = b2_call($call_url, $headers, $read_file);
            return $result; // Return the result
        }