How to convert Complex forms ?

[wangfan0840]

hi!

<input name="user[email]" value="jsmith@example.com">
 <input name="user[pets][]" type="checkbox" value="cat" checked>
 <input name="user[pets][][cat][]" type="checkbox" value="cat1" checked>
 <input name="user[pets][][cat][]" type="checkbox" value="cat2" checked>
 <input name="user[pets][]" type="checkbox" value="dog" checked>
 <input name="user[pets][]" type="checkbox" value="bird">

i want to got a json like:
{user: {email: "jsmith@example.com", pets: [cat:["cat1","cat2"], "dog"]}}
but l got a json :
{ "user":{"email":"jsmith@example.com","pets":["cat", "dog",null,{"cat":[null,null,"cat2"]} ]}
please tell me how to get the correct json string !
thanks!

[macek]

This is not valid

[cat:["cat1","cat2"], "dog"]