這樣的json如何產生啊

這樣的json怎麼產生啊，
目標：產生一個樹型菜單。
資料庫，如下：

我在後台，如何用Php產生如下josn，那他們顯示出來啊？
json格式如下：

var json = [{"name":"*a","list":[
{"name":"**a","url":"#a1"},
{"name":"**aa","list":[{"name":"***a","url":"#a11"},{"name":"***aa","list":[{"name":"****a","url":"#a111"},{"name":"****aa","list":[{"name":"*****a","url":"#a1111"},{"name":"*****aa","url":"#a1112"}]}
]},
{"name":"***aaa","url":"#a13"},{"name":"***aaaa","url":"#a14"}]},{"name":"**a","url":"#a3"}]},
{"name":"*b","list":[
{"name":"**b","url":"#b1"},
{"name":"**bb","list":[
{"name":"****b","url":"#b111"},
{"name":"****bb","url":"#b112"}
   ]
},
]
},
{"name":"*c","list":[
{"name":"**c","url":"#c1"},
{"name":"**cc","url":"#c2"}
]
},
{"name":"*d"}
   ]

------解決思路----------------------
參考：
http://bbs.csdn.net/topics/390364669
http://bbs.csdn.net/topics/390524563

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