undefined error with ajaxcall to receive json data - php

Question

my problem is that I
can not solve this problem
If I call the php script, all I get is an undefined error
this is the code I use for testing AND
this is the original code from the creator that is giving me a headache
function startJsonSession(){
$.ajax({ url: "jsontest.php?action=startjson",
cache: false,
dataType: "json",
complete: function(data) {
username = data.username;
alert(username);
}
});
}
//phpscript
if ($_GET['action'] == "startjson") { startJson(); }
function startJson() {
header('Content-type: application/json');
$items = '';
echo json_encode(array(
"username" => "bob",
"items" => array( "item1" => "sandwich",
"item2" => "applejuice"
)
));
}
thanks, Richard
edited my question because:
this function returns the json data in a different way
and therefore the solution presented below, does not have the same outcome.
function startChatSession() {
$items = '';
if (!empty($_SESSION['openChatBoxes'])) {
foreach ($_SESSION['openChatBoxes'] as $chatbox => $void) {
$items .= chatBoxSession($chatbox);
}
}
if ($items != '') {
$items = substr($items, 0, -1);
}
header('Content-type: application/json');
?>
{
"username": "<?php echo $_SESSION['username'];?>",
"items": [
<?php echo $items;?>
]
}
<?php
exit(0);
}

Answer 1

I recreated with your code and figured it out. The object being returned is of type XMLHttpRequest. Its got a property called responseText holding a json string with the data.
so this works..
var decodedData = eval("(" + data.responseText + ")");
username = decodedData.username;
alert(username);
A bit messy but it does the trick :-)
p.s If it helps, I figured it out using firebug in firefox and sticking a breakpoint in the js code
Edited below:
Without wanting to do the eval, you could use this and it works:
$.getJSON("json.php?action=startjson",
function(data) {
username = data.username;
alert(username);
}
);
Edited to show what I did with the success function:
$.ajax({
url: "json.php?action=startjson",
cache: false,
dataType: "json",
success: function(data) {
username = data.username;
alert(username);
}
});

Answer 2

Is username a global variable?
If not you should prepend the "var" keyword.
username = data.username -> var username = data.username;

Answer 3

At the end I got it working.
I installed firebug and saw that the php script was returning html headers instead off json.
All off the sudden it started working, I really would like to know what the problem was, but I can't tell you.
Anyway, thanks for sticking so long, David

Answer 4

also what I don't understand is that it breaks out off php mode, instead of echoing it back like it's done with xml
?>
{
"username": "<?php echo $_SESSION['username'];?>",
"items": [
<?php echo $items;?>
]
}
<?php
is this the same as above (object array containing literal array)?
echo json_encode(array(
"username" => "bob",
"items" => $items
)
));
}