CURL: Save response to string

[Nrgyzer]

Hi guys,

I know... there's a lib for curl but I'm using an old CURL-binding for D... 
I've the following problem: I'm sending my login data to
a web page and I want store the response of curl_easy_perform() in a string. So 
I'm using the following few lines to do that:

string temp;

size_t callback(char* ptr, size_t size, size_t, nmemb, string* stream) {
   temp ~= *ptr;
   // or: How can I append ptr to my stream?
   // When I use '*stream ~= cast(char) ptr;' I get an memory violation...
}

void main() {
        CURL* curl = curl_easy_init();

        curl_httppost* post;

        curl_formadd(&post, &last, CURLFORM_COPYNAME, toStringz("username"), 
CURLFORM_COPYCONTENTS, toStringz("username"),
CURLFORM_END);
        curl_formadd(&post, &last, CURLFORM_COPYNAME, toStringz("password"), 
CURLFORM_COPYCONTENTS, toStringz("password"),
CURLFORM_END);
        curl_easy_setopt(curl, CURLOPT_HTTPPOST, post);
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, &callback);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, &temp);
        curl_easy_setopt(curl, CURLOPT_URL, 
toStringz("https://myURL.tld/login.php";));
        curl_easy_perform(curl);
        writeln(temp);
}

But when I run the code, temp is completely empty... does anyone know how to 
fix that or what I'm doing wrong?

Thanks for all suggestions!