为timeline.js构建所需JSON输出的多维数组

timeelinejs需要一个指定的JSON格式。到目前为止，使用这个php代码，我能够生成如下所示的输出:

$rs = mysql_query("SELECT filename, data AS added,  f.image as media, f.info_hash AS hash, c.name AS category FROM xbtit_files f LEFT JOIN xbtit_categories c ON f.category = c.id WHERE f.uploader =  '2' ORDER BY added DESC"); 
$json_arr = array();
while($row = mysql_fetch_array($rs)) { 
if (strlen(htmlspecialchars($row[filename])) > 30)
  $t_name  = substr(htmlspecialchars($row[filename]), 0, 30)."...";
else
  $t_name  = htmlspecialchars($row[filename]);
$row_arr['credit'] = $row['hash'];
$row_arr['caption'] = $row['category'];
$row_arr['media'] = $row['media'];
$row_arr['headline'] = $t_name;
$row_arr['startDate'] = $row[added];
array_push($json_arr,$row_arr);
} 
$json = '{"timeline":
    {
        "headline":"UPLOADER1",
        "type":"default",
        "text":"Show all uploads of this uploader",
        "asset": {
            "media":"http://localhost/torrent/torrentimg/49ac3aa95ec6d2ae56772a158b41d4aa62a7b78c.jpg",
            "credit":"Credit Name Goes Here",
            "caption":"Caption text goes here"
            },
        "date":
            '.json_encode($json_arr).'
    }}';
echo $json;

输出如下:

{
"timeline": {
    "headline": "UPLOADER1",
    "type": "default",
    "text": "Show all uploads of this uploader",
    "asset": {
        "media": "http://localhost/torrent/torrentimg/49ac3aa95ec6d2ae56772a158b41d4aa62a7b78c.jpg",
        "credit": "Credit Name Goes Here",
        "caption": "Caption text goes here"
    },
    "date": [
        {
            "headline": "Avatar",
            "startDate": "2012-06-26 12:03:13"
        },
        {
            "headline": "Rio BRRIP x264-1080p-2011",
            "startDate": "2012-06-26 11:59:19"
        },
        {
            "headline": "The Number 23 (2007)",
            "startDate": "2012-06-26 11:50:44"
        },
        {
            "headline": "Fate Stay night",
            "startDate": "2012-06-26 11:41:01"
        }
    ]
}
}

我怎么能得到这样的东西:

{
"timeline":
{
    "headline":"UPLOADER 1",
    "type":"default",
    "text":"Name of the Uploader",
    "startDate":"2012,1,26",
    "date": [
        {
            "startDate":"2012,2,30",
            "headline":"Hanky Panky (Torrent Name)",
            "text":"<p>Some description of the torrent.</p>",
            "asset":
            {
                "media":"Poster.jpg",
                "credit":"",
                "caption":""
            }
        },
        {
            "startDate":"2012,2,18",
            "headline":"Torrent Name 2",
            "text":"This movie was released on... The actors are....",
            "asset":
            {
                "media":"Poster1.jpg",
                "credit":"",
                "caption":"Directed and Edited by Matt Mayer, Produced by Seth Keim, Written by Eliot Glazer. Featuring Eliot and Ilana Glazer, who are siblings, not married."
            }
        }
    ]
}
}

注意:在对象资产中有JSON对象。如何才能做到这一点?有人能帮忙吗?