Connecting MySQL By HTTPClient Via PHP?

I'm trying to create a login function in my new App.I wrote a php file in my server to be an interface between my App and MySQL.

Quote:

private void connectPHP(){
try {
HttpClient client = new DefaultHttpClient();[code].....

I expect responseMessage will equal to "Success", but as result it returns a NULL value.

1. I'd try the php file in a web browser and it operates normally, I'm sure the problem came from the JAVA code.

2. I'd try to use the response.getStatusLine().getStatusCode() method to check the HTTP status code, but it doesn't return any number.