PHP backend for JSON interaction with Android

Some friends said that they use the code of the blog in the following code error, there is builder.tostring () can not be converted to JSON object errors.

Jsonobject jsonobject   = new Jsonobject (builder.tostring ());

and I'm not wrong about my own experiment. So the friend built PHP server-side code for some checks, and finally found the problem lies . So write this down, hoping to help the vast number of students stepping into the same pit

This involves PHP's Json_decode function, which is why my friends are making mistakes.

Now write the code I have tested successfully, I am in the Android sent to the PHP server is a jsonobject,{"name": "Lala"}, the corresponding entity name is "Userjson", that is, the following code

Jsonobject Jo = new Jsonobject ();

        Jo.put ("name", "Test");

Params.add (New Basicnamevaluepair ("Userjson", Jo.tostring ()));

At this point, my server-side code is

<?php      $json _string = $_post ["Userjson"];  $user = Json_decode ($json _string,true);//True plus converts a JSON string from Android to an associative array

  $arr = Array (          ' user_id ' = = $user ["name"]        );  $str = Json_encode ($arr);      Echo ($STR);  ? >

at this time on Android will not be reported can not be converted to Jsonobject error, of course I can also on the server side to send Jsonarray to the server. That is, [{"Name": "Lalala"},{}]

In this case, the above PHP code will not be executed correctly to the last sentence, this time we want to change the code to

<?php      $json _string = $_post ["Userjson"];  $user = Json_decode ($json _string,true);//True plus converts the JSON string from Android to an associative array  $arr = Array (          ' user_id ' = > $user [0]["name"]        );  $str = Json_encode ($arr);      Echo ($STR);  ? >

Why do you want to change it? The reason is very simple, and when we add true to the Json_decode function, we convert the received $json_string into associative arrays. For example, the first example, Jsonobject will be transformed into a

Array (1) {["Name"]=>string ("Test")}

So you can read the string "test" with $user["name", and the result of conversion in example two is

Array (2) {[0]=>array (1) {["Name"]=>string ("Lala")}[1]=>array (0) {}}

This time using $user["name"] will be wrong, and need to use $user[0]["name"] to read to "Lala" string

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