How to bring data from a JSON webservice on Android

I wanted someone to explain how to do this. I have the following code in PHP and wanted to bring it to Android, returning the person's name. Can be in an Array ... The problem is that I can not get this data.

$f = fopen('POST_DATA.txt', 'a');
fwrite($f, 'ID: '.$id."\r\n");
$id = uniqid( time() );
fwrite($f, 'Nome: '.$_POST['nome']."\r\n");
fwrite($f, 'Cpf: '.$_POST['cpf']."\r\n");
fwrite($f, 'Bairro: '.$_POST['bairro']."\r\n");
fwrite($f, 'E-mail: '.$_POST['email']."\r\n");
fwrite($f, 'Telefone: '.$_POST['telefone']."\r\n\r\n");

fclose($f);

echo 'Dados enviados com sucesso';