Question

I had some problem understanding the following line of code. What exactly does it do and how does it help me query the database from android

$q=mysql_query("SELECT * FROM people WHERE birthyear>'".$_REQUEST['year']."'");
while($e=mysql_fetch_assoc($q))
    $output[]=$e;
print(json_encode($output));

I know the initial part of it means select every record from table people where birthyear…

But after that I get confused. I am calling this php function from android using http post

ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("year","1980")); 
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost("http://10.0.2.2/retrieve.php");
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse response = httpclient.execute(httppost); 
HttpEntity entity = response.getEntity();
is = entity.getContent();

Where is an input stream. Can someone help me out?

Answer 1

The PHP code queries the database and constructs a JSON output, which it sends to the calling client. Try calling the php from a browser (put the URL in the address bar) – and you should get the JSON back.

On the Android side, java code is using HTTPClient wrapper to call your php and get the response. Socket (HTTP connection) InputStream is handled internally by HttpClient when you call relevant methods. From your point of view, all you need to do is deal with the content of the entity.

You can just open the input stream from the entity (your is variable) and read the data from it:

InputStream is = entity.getContent();

then read the content of the stream as you normally would. You should get the json as was sent by the php.

PHP gets the value of required minimum year from year request parameter. In android, a NameValuePair is created with name=year and value=1980. This NameValuePair is passed as POST parameter in the form year=1980 to the PHP code. Again, this is handled internally by the HTTPClient wrapper class. Then the PHP code reads the value of request parameter “year” to get the minimum value for the query.