Sample "code":
Entering the following into the address bar of your browser
http://www.mywebpage.com/test.php?name=value&name2=value2&name3=value3
or clicking a link such as
<a href="http://www.mywebpage.com/test.php?name=value&name2=value2&name3=value3">link</a>
or sending a form such as
<form method="get" action="http://example.com/someresource">
<input name="this" value="is the query string" />
<input type="submit" name="submit" value="submit"
</form>
A request for
http://example.com/somresource?this=is+the+query+string
means the query string ends up as element key => value pairs in PHP's $GET array:
$GET['this'] === 'is the query string'
Just like a post request with the following ends up as key => value pairs in the $POST array
<form method="post" action="http://example.com/someresource">
<input name="this" value="is not the query string" />
<input type="submit" name="submit" value="submit"
</form>
$_GET['post'] === 'is not the query string'
As long as your app requests the resource over http the query string will work (at least unless you have an excessive amount data). If you don't like it, the other way is a post request, which doesn't necessarily require a form either. Your app could create a post request on its own as well.