json_decode fails - php

Question

I'm fairly new to json, and I'm having an issue with json_decode. I think I know why, but I haven't been able to sort out how to fix it.
Basically, I have a URL that supplies json info. I grab it using cURL, and return it as a PHP variable, and that's working just fine. I can print_r out all the info I want. However, when I use json_decode($json, true), it returns NULL.
I THINK it's because, technically, what's being returned is not a string, but more like an object - and I can't sort out how to grab the contents of that object.
For example, when I return the json stuff as a php variable:
print_r($json);
The output returned looks like so (I won't do it exactly, because it's HUGE, so I'll show you the layout to keep it simple)
MyThing.returnedItems({MyThing.returnedItems({
"projects":[{
"completed":"2010-12-21",
"status":"finished",
"favorited":0,
"started":"2010-12-20",
"percentage":78,
"permalink":"slug to post",
"size":"One size",
"thumbnail":{"src":"full path to full size image",
"medium":"full path to thumbnail"},
"name":"Some title here",
"notes":"description here",
"url":"URL to page",
"comments":0},
So you can see it's like a nested array. I don't mind that, but I'd like to be able to access all the key/value pairs of these arrays as PHP variables. But it seems because of the "MyThing.returnedItems()" surrounding it, it doesn't see it as a string to decode, so I get a NULL value every time.
Anyone know what I'm missing here? Once I figure out how to grab the stuff inside there, I think I've got it (simple foreach or whatnot to get the rest of the variables as needed), but I just can't seem to get in there.

Answer 1

This is valid JSON
{
"item1": [
{
"something": [],
"something else": "some value"
}
],
"another fun thing": [
{
"more fun": "fun value 1",
"even more!": "fun value 2"
}
],
"item2": {
"another thing": "another value"
}
}
This is not!
MyThing.returnedItems({
"item1":[{"something:[],
"something else": "some value"},
"another fun thing": [{"more fun": "fun value 1",
"even more!": "fun value 2"}]
],
"item2":{"another thing": "another value"}
})
Its a javascript method call

Answer 2

Okay, I just wanted to add that you all REALLY helped me out. Especially MaX, because by knowing the "official term" of what was happening, I had better searches and ended up finding some really interesting code that eventually landed me my solution. However, I did discover the reason why I was having my json wrapped in that weird function method call: the URL that the site gave me to access their API actually had that call in it, so it was returned wrapped in it. In other words, the json file URL I had was like so:
somesite.com/apicall.json?key=1234567890&callback=MyThing&version=0...
so as soon as I removed that "callback" section - BAM the json was no longer wrapped, and a whole new world of foreach functions opened up to me. So, even though the solution ended up being a REALLY stupid oversight on my part, I wanted to thank you all for your input, because I learned a whole lot of stuff I wasn't planning to today XD
Oh, and the code that actually ended up working (after I got rid of the callback part of the URL, because json_decode was still returning NULL on me) was this:
$data = json_decode(file_get_contents($json), true);
print_r($data); // array of everything available for me to mess with!
Thanks again for your help, everyone :) I REALLY appreciate it!