Cant Post data form android to php api - php

Question

I have created an API using PHP and MYSQL and now i want to get data in Android.
My API works fine if i pass static data to it and run in browser but when i try to post data to android it throws an exception. I want to post username password for mysql database and a word through which it will return the word and definition in JSON format. Again as a I mentioned it works fine when i add static data in my php script but not working when posting through android. Here's what i've done so far
PHP
<?php
header('Content-type: application/json');
$username=urlencode($_POST["username"]);
$pass=urlencode($_POST["pass"]);
$connect = mysqli_connect('pakscrabble.ipowermysql.com', $username, $pass,'csw19');
if (!$connect) {
die('Could not connect: ' . mysql_error());
}
$w=urlencode($_POST["wordtosearch"]);
$q="select * from words where word='".$w."' ";
$query=mysqli_query($connect,$q);
$dict_data = array();
while($row=mysqli_fetch_array($query))
{ $dict_data[] = array(
'word' => $row[0],
'def' => $row[1] );
}
echo "<pre>";
print_r(json_encode($dict_data));
echo "</pre>";
?>
Android
String urlString = params[0]; // URL to call
String username = params[1];
String pass=params[2];
String wordtosearch=params[3];
OutputStream out = null;
try {
URL url = new URL(urlString);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("POST");
out = new BufferedOutputStream(urlConnection.getOutputStream());
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out, "UTF-8"));
String data = URLEncoder.encode("username", "UTF-8")
+ "=" + URLEncoder.encode(username, "UTF-8");
data += "&" + URLEncoder.encode("pass", "UTF-8") + "="
+ URLEncoder.encode(pass, "UTF-8");
data += "&" + URLEncoder.encode("wordtosearch", "UTF-8")
+ "=" + URLEncoder.encode(wordtosearch, "UTF-8");
writer.write(data);
writer.flush();
writer.close();
out.close();
urlConnection.connect();
JSONObject responseJSON = new JSONObject();
Toast.makeText(c, String.valueOf(responseJSON.getString("def")), Toast.LENGTH_SHORT).show();
String loginMessage = responseJSON.getString("loginMessage");
String userName = responseJSON.getString("user");
} catch (Exception e) {
Toast.makeText(c, e.getMessage(), Toast.LENGTH_SHORT).show();
return "something happened";
}
return "Hello World!";
Never reaches the Hello World part and throws an exception