客户端应该如何将json数据发送给PHP

I have used php for server side and my client(A java program) sends a post request with json data as parameter. I am able to receive the data but the jsonData is no decoding. I am sending a valid JSON. Below is my Client program.

public class ExampleHttpPost
{
  public static void main(String args[]) throws ClientProtocolException, IOException
  {
    HttpPost httppost = new HttpPost("http://localhost/hello.php");
    List<BasicNameValuePair> parameters = new ArrayList<BasicNameValuePair>();
    try {
        parameters.add(new BasicNameValuePair("data", (new JSONObject("{\"imei\":\"imei1\"}")).toString()));
    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    httppost.setEntity(new UrlEncodedFormEntity(parameters));
    HttpClient httpclient = new DefaultHttpClient();
    HttpResponse httpResponse = httpclient.execute(httppost);
    HttpEntity resEntity = httpResponse.getEntity();

    // Get the HTTP Status Code
    int statusCode = httpResponse.getStatusLine().getStatusCode();

    // Get the contents of the response
    InputStream input = resEntity.getContent();
    String responseBody = IOUtils.toString(input);
    input.close();

    // Print the response code and message body
    System.out.println("HTTP Status Code: "+statusCode);
    System.out.println(responseBody);
  }
}

And my hello.php

<?php
    $data = $_POST['data'];
var_dump($data);
$obj = json_decode($data);
if($obj==NULL){
    echo "Decoding error";
}
echo $obj['imei'];
?>

Output :

HTTP Status Code: 200
string(20) "{\"imei\":\"imei1\"}"
Decoding error

It seems like your Java Application is adding slashes to the string or as suggested in the comments the PHP app is probably adding slashes to the quotes to avoid SQL injection Try if you can get it to work by adding

$data = stripslashes($data);

Above the json_decode part