javascript convert object string to string - php

Question

I cannot convert JS object to exact string, my code:
jsonObj['payment_value']=100.10;
jsonObj['payment_date']="2012-06-15";
jsonObjStr = JSON.stringify(jsonObj);
alert(jsonObjStr);
$.post("test", jsonObjStr.toString(), function(output){
alert(output);
});
first alert displays:
{"payment_date":"2012-06-15","payment_value":100.1}
and in function test (i'm using codeigniter framework) it should print "payment_date" and "payment_value", code like this:
echo $this->input->post("payment_value");
echo $this->input->post("payment_date");
which is equvalent in "clear" php to:
echo $_POST["payment_value"];
echo $_POST["payment_date"];
but second alert displays clear string.
If I put
{"payment_date":"2012-06-15","payment_value":100.1}
instead of jsonObjStr.toString() it works fine
Does anyone knows how to fix it WITHOUT using json_decode? I need to have posted values in this format, not in other array
So i need to convert jsonObjStr exact to string (something inversely to function eval())
Thank in advice

Answer 1

According to $.post docs, second argument should be map or query string:
map example:
{
"payment_date":"2012-06-15",
"payment_value":100.1
}
query string example:
'payment_date=2012-06-15&payment_value=100.1​​​'
When you use JSON.stringify, then you get:
'{"payment_date":"2012-06-15","payment_value":100.1}'
which is invalid query string. So the solution is: do not stringify anything, pass the object itself as 2nd argument:
jsonObj['payment_value']=100.10;
jsonObj['payment_date']="2012-06-15";
$.post("test", jsonObj, function(output){
alert(output);
});