null or not an object in IE

[macaco]

I have developed a webapp that works very good on firefox and opera, but on IE I keep getting an error message.

I use AJAX to communicate with a PHP file that queries a MySQL database and returns the information in JSON.

function sendQuerystring2(url,mod,columna)
{
    http2.open("GET", url, true);
    if (mod == "tabla") {
        http2.onreadystatechange = function (){
            if (http2.readyState == 4) {
                hide('cargando');
                if (http2.status == 200) {
                    obj_detalle = eval('(' + http2.responseText + ')');
                    crear_tabla(columna);
                }
            } else {
                show('cargando');
            }
        }    
    }

{"items":[{"id":"1","titulo":"Prueba"}]}

obj_detalle['items'][0].id, is "null or not an object" in IE, while in firefox works perfectly.

I have tried an alert(http2.responseText) and it has the correct content.

does anyone know a fix to this?
many thanks.

[iam_clint]

why are you using eval?

[macaco]

why are you using eval?

because it's the way to use JSON. it turns the sent string into a javascript object.

I have also tried with POST instead of GET.. but still getting the same results.

[iam_clint]

i guess i don't understand why a string needs to be an object?

[macaco]

because it's not only this:

{"items":[{"id":"1","titulo":"Prueba"}]}

there are many items with many other "properties". and I think this is the best way to parse this information. something similar to XML in a way. I can access any property like this:

obj_detalle.items[itemNumber].property

though I it is not working on IE.