setcookieの正しい使い方

if (value && value_len == 0) {
        /*
         * MSIE doesn't delete a cookie when you set it to a null value
         * so in order to force cookies to be deleted, even on MSIE, we
         * pick an expiry date 1 year and 1 second in the past
         */
        time_t t = time(NULL) - 31536001;
        dt = php_format_date("D, d-M-Y H:i:s T", sizeof("D, d-M-Y H:i:s T")-1, t, 0 TSRMLS_CC);
        snprintf(cookie, len + 100, "Set-Cookie: %s=deleted; expires=%s", name, dt);
        efree(dt);
    } else {
        snprintf(cookie, len + 100, "Set-Cookie: %s=%s", name, value ? encoded_value : "");
        if (expires> 0) {
            strlcat(cookie, "; expires=", len + 100);
            dt = php_format_date("D, d-M-Y H:i:s T", sizeof("D, d-M-Y H:i:s T")-1, expires, 0 TSRMLS_CC);
            strlcat(cookie, dt, len + 100);
            efree(dt);
        }
    }