php转换成json数据格式?

Question

{ "programmers": [ { "firstName": "Brett", "lastName":"McLaughlin", "email": "aaaa" }, 
{ "firstName": "Jason", "lastName":"Hunter", "email": "bbbb" }, 
{ "firstName": "Elliotte", "lastName":"Harold", "email": "cccc" }
],
"authors": [ 
{ "firstName": "Isaac", "lastName": "Asimov", "genre": "science fiction" }, 
{ "firstName": "Tad", "lastName": "Williams", "genre": "fantasy" }, 
{ "firstName": "Frank", "lastName": "Peretti", "genre": "christian fiction" } 
], 
"musicians": [ 
{ "firstName": "Eric", "lastName": "Clapton", "instrument": "guitar" }, 
{ "firstName": "Sergei", "lastName": "Rachmaninoff", "instrument": "piano" } 
] } 
这样的数据格式是怎么样转换的
我从数据库查出来的数据直接转换的话是
[
{ "firstName": "Eric", "lastName": "Clapton", "instrument": "guitar" },
{ "firstName": "Sergei", "lastName": "Rachmaninoff", "instrument": "piano" }
]
这样的！
因为是分开查询三个表 ，把它组成一条json数据，应该怎么去写

Answer 1

　json和php数组 格式的互相转换，参考如下：　　$php_json = json_encode($json_arr); //把php数组格式转换成 json 格式的数据　　echo $php_json;　　$php_json = json_decode($php_json); //再把json格式的数据转换成php数组　　print_r($php_json);　　json数组　　$json = '[{"id":"22","name":"33","descn":"44"}]'; //json格式的数组转换成 php的数组　　$arr = (Array)json_decode($json);　　echo $arr[0]->id; //用对象的方式访问