解析用户详细信息失败

Question

ArrayList<NameValuePair> dataToSend = new ArrayList<>();

dataToSend.add(new BasicNameValuePair("email", email));

try{
    HttpParams httpRequestParams = getHttpRequestParams();
    HttpClient client = new DefaultHttpClient(httpRequestParams);
    HttpPost post = new HttpPost(SERVER_ADDRESS + "display_userAdvertisement.php");

    post.setEntity(new UrlEncodedFormEntity(dataToSend));
    client.execute(post);

My PHP code

php
$con=mysql_connect('localhost','synaptic','12345');

//define ('DB_HOST', 'xxx.xx.xxx.xx:80');
mysql_select_db("bruhbmvr_register",$con);

$email = $_POST['email'];

$sql = "select * from post_ads WHERE email = '$email'"; 
$result = mysql_query($sql);
$json = array();
if(mysql_num_rows($result)){
    while($row=mysql_fetch_assoc($result)){
        $json['userinfo'][]=$row;
    }
}
mysql_close($con);
echo json_encode($json); 
?>

I'm trying to parse the email from the Android apps to the PHP file, but it is empty.

My question is how do I parse the email to PHP, and then directly show the details of the email in JSON format?