php - How to save a record in mongo db sub document using cakephp -

i have structure in mongodb:

{     id: 1,     students:[          {              id:1,              is_allowed: true          },          {              id:2,              is_allowed: true          },     ] } 

my problem dont know how add new record add student using cakephp.

with mongodb current version, cant add/delete record students. can update whole students using this. if have integrated ichikaway plugin can use $this->save() have set collection id updating purpose work how 'cakephp` functionality works mysql.