Connection to server from client app Android

Question

Good evening to all,

I would insert a string on db that hosted in my web page.

I've created a php file that with a GET method pass the param that I would insert.

This method on the browser work but if i call it on Android app with the following code not work. Why? Can you help me?

inviaButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view){
                String prova = "ciao";

                try {

                    URL paginaURL = new URL("http://www.differenziapp3.altervista.org/insertSegnalazione.php?descr=" + prova);
                    HttpURLConnection con = (HttpURLConnection) paginaURL.openConnection();
                } catch (Exception e) {}
            }
        });

This is php file :

<?php
include("connessione.php");

$descr=$_GET['descr'];
$idp="vuoto";
$idp2=0;

$query="INSERT INTO segnalazione(foto,data,ora,lati,longi,descrizione)VALUES
('".$idp."','".$idp."','".$idp."','".$idp2."','".$idp2."','".$descr."')";
mysql_query($query);

?>

Thanks for all