What technology are they using ?

Here are some android app stores...

http://www.androidzoom.com/
http://www.appbrain.com/
http://www.androlib.com/

These sites get contents like version, size, description, etc., from official android market place...

What technology they are using to achieve this... I am going to make such site using PHP... what i want to use ?

 

I suppose they are using the android market api:

http://code.google.com/p/android-market-api-php/

 

they are using data fetching techniques to copy data from official android site to their site, you can also create same site and get data from original android site.

 

what are the data fetching techniques ??? give some ??

 

You can create your own data fetching mechanism using PHP. For that, you'll have to play a bit with cURL and preg functions.

cURL is used for pulling the whole content of a remote page and preg function help in extracting a particular piece of text.

Here's a rough idea.

$text = get_via_curl("http://some-url.com/some-android-app-page.htm");
$app_version = get_app_version_via_preg($text);

Code (markup):

Of course, you would need to learn and them create your own get_via_curl() and get_app_version...() function.

If cURL is not available on your server, file_get_contents() with stream_context_create() would come in handy.

If official API is available for pulling data, just go for it.

 

Is it possible to make money selling Android apps via API?

 

Why not ? depends on the quality of app and how famous it grows.