merge values of unique keys of json string - php

Question

i have a json output code like this:
{"a":{"p1":"1"},"a":{"p2":"2"},"b":{"b1":"b2"}}
how to convert it to below using javascript or jquery or php ?
{"a":{"p1":"1","p2":"2"},"b":{"b1":"b2"}}
EDIT:
i generate json code by this code:
parts2.push('"'+$(this).attr('alt')+'":{"'+$(this).attr('title') + '"' + ":" + '"'+$(this).attr('value') + '"}' );
however $(this).attr('alt') maybe repeated in loop and i want to prevent duplicate key and instead append value to that key

Answer 1

Each property of an object is supposed to have a unique key name. If you try to parse JSON with duplicate key names, only the last occurring value is used, so it isn't possible to parse this with the native JSON.parse and still expect data to be preserved.
As per your edit, you can prevent the duplicates from ever occurring:
var obj = {};
if typeof obj[$(this).attr('alt')] == "undefined"
obj[$(this).attr('alt')] = {};
obj[$(this).attr('alt')][$(this).attr('title')] = $(this).attr('value');
parts2.push(JSON.stringify(obj));

Answer 2

You should merge the value before you generate the JSON string or you have to implement a JSON parser yourself to parse your JSON.
In http://www.ietf.org/rfc/rfc4627.txt?number=4627:
The names within an object SHOULD be unique

Answer 3

Instead of stringing the pseudo-JSON, just create an object, fill that, and stringify the object when you send it:
var parts = {};
$('.foo')each(function()
{//the loop, here parts is being filled
parts.[$(this).attr('alt')] = parts.[$(this).attr('alt')] || {};//initialize to object if property doesn't exist
parts.[$(this).attr('alt')] = [$(this).attr('title')] = $(this).attr('value');
});
//make JSON:
partsJSON = JSON.stringify(parts);
//{a:{p1:foo,p2:bar},b:{p3:foobar}} or something