Invalid JSON in Chrome, no problem in Firefox (so strange!)

Question

All keys were double quoted. The whole element was an object. Firefox runs it well but Chrome reports "invalid JSON". Why?

This is full code.

///////////// PHP ////////////////
public function listAlbumAction()
{
    $params = $this->_getAllParams();
    $albums = $this->_album->getAlbumList($params['albumType'], $params['from'], $params['numberOfAlbums']);
    echo json_encode(array("code" => 0, "data" => $albums));
}

///////////////////////////////// JQuery ///////////////////
function loadAlbums()
{
    $.ajax({
        type: 'GET',
        url: '/about-photo/list-album',
        data: {albumType: selectedAlbumType, from: currentPageIndex * numOfAlbumsPerPage, numberOfAlbums: numOfAlbumsPerPage},
        success: function(json) {
            var obj;
            var data;
            try {
                obj = $.parseJSON(json);
                data = obj.data;                                    
            } catch(e) {
                alert(e);
            }               

            if(obj.code == 0) {
                // get number of albums
                var num = data.length;

                // remove old list content
                $('#albumListContent').remove();

                var albumListHTML = '';
                albumListHTML += '<div id="albumListContent">';

                for(var i = 0; i < num; ++i) {                          
                    albumListHTML += '<div id="w' + data[i].album_id + '" class="imgWrapper">';
                    albumListHTML += '<img id="a' + data[i].album_id + 
                                     '" class="albumImg" width="150px" src="' + 
                                     data[i].album_cover + '" alt="not found" title="' + 
                                     data[i].album_name + '"/>';                                             
                    albumListHTML += '<div class="albumTitle">' + data[i].album_name + '</div>';
                    albumListHTML += '</div>';                      
                }

                albumListHTML += '</div>';
                $('#albumListContentWrapper').html(albumListHTML);

                addAlbumHandler();
                addPhotoEffects('.albumImg');                   
                addImgErrorHandler('.albumImg');
            }
        }
    });
}

Edit: JSON output from Chrome (FirebugLite):

    {"code":0,"data":[{"album_id":42,"album_name":"Best album","album_type":"photo","create_date":"09-05-2011 5:48:40","album_cover":"\/x\/media\/6.jpg","description":"Something here"},{"album_id":56,"album_name":"Test album","album_type":"photo","create_date":"09-05-2011 19:27:50","album_cover":"\/x\/media\/44227440_2f1f369517.jpg","description":"apples"},{"album_id":59,"album_name":"Album for something","album_type":"photo","create_date":"10-05-2011 16:19:03","album_cover":"\/x\/media\/apple-howto.jpg","description":"zzz"},{"album_id":62,"album_name":"Vietnam - Thailand - AFF Suzuki cup 2007","album_type":"photo","create_date":"17-05-2011 14:30:32","album_cover":"\/x\/media\/pwjps1231986828.jpg","description":""},{"album_id":63,"album_name":"CS","album_type":"photo","create_date":"17-05-2011 15:24:01","album_cover":"\/x\/media\/apple-logo.jpg","description":""},{"album_id":64,"album_name":"It works","album_type":"photo","create_date":"17-05-2011 15:24:56","album_cover":"\/x\/media\/it_works.png","description":""}]}

JSON output from Firefox (Firebug):

{"code":0,"data":[{"album_id":42,"album_name":"Best album","album_type":"photo","create_date":"09-05-2011 5:48:40","album_cover":"\/x\/media\/6.jpg","description":"Something here"},{"album_id":56,"album_name":"Test album","album_type":"photo","create_date":"09-05-2011 19:27:50","album_cover":"\/x\/media\/44227440_2f1f369517.jpg","description":"apples"},{"album_id":59,"album_name":"Album for something","album_type":"photo","create_date":"10-05-2011 16:19:03","album_cover":"\/x\/media\/apple-howto.jpg","description":"zzz"},{"album_id":62,"album_name":"Vietnam - Thailand - AFF Suzuki cup 2007","album_type":"photo","create_date":"17-05-2011 14:30:32","album_cover":"\/x\/media\/pwjps1231986828.jpg","description":""},{"album_id":63,"album_name":"CS","album_type":"photo","create_date":"17-05-2011 15:24:01","album_cover":"\/x\/media\/apple-logo.jpg","description":""},{"album_id":64,"album_name":"It works","album_type":"photo","create_date":"17-05-2011 15:24:56","album_cover":"\/x\/media\/it_works.png","description":""}]}

I checked it with http://jsonlint.com/ and it says "Valid JSON"

Edit:

Source viewed from Chrome:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 

Answer 1

You have a Unicode Byte Order Mark at the beginning of your PHP file. Because of this, and because it's before the opening <?php, it gets sent to the client at the beginning of your JSON. This will make your JSON invalid, as those characters shouldn't appear at the beginning of the JSON data. Some browsers cope with it fine; other browsers, such as Chrome, are fussier and complain.

Removing the Byte Order Mark by saving the file without that option set in your editor (how to do this is editor-dependent) will solve your problem.

(You'd probably also find that header() and other PHP functions that send headers wouldn't work in your PHP file, either, giving you the error that output has already started, again because the BOM would have been sent before your PHP started being interpreted.)

Answer 2

My guess (based on the difference between the Chrome and Firefox outputs you provided) would be that you've got some leading (or trailing) spaces and/or line breaks sneaking into your PHP output.

You've only provided the PHP for the relevant functions, but check that you haven't got any blank space before or after the <?php and ?> tags, both in your main program and any other PHP files loaded with include() or require().

Its a fairly common problem with PHP code. In a normal HTML page it doesn't really matter (you end up with a load of spurious white space, but it doesn't affect the rendering), but when outputting other types of data it can make the difference between it being valid or not. This is especially true if you're outputting binary data. I've not seen this issue before with JSON, but the blank spaces at the begining of the string you quoted are a classic sign of this sort of thing.