php - Update item inside a mongodb object -

i'm trying save() record inside object. problem mongocursor()-errors or unexpected 'array' (t_array). instance:

this mongodb-collection:

[   {     "id": "dfk15ale12",     "keys": {       "gcm_key": "abc",       "app_secret": "123"     }   } 

]

i want update gcm_key inside keys, php code:

$db->apps->save(     array("_id" => $update['_id'])     array("$push" => 'keys.gcm_android' => $gcm_android); ); 

this gives me following error:

parse error: syntax error, unexpected 'array' (t_array) in c:\xampp\htdocs\api\update.php on line 3 

i have googled , looked here on stack find answers, , i've found nothing. maybe i've missed something. don't know, correct mongodb cursor , easiest way save() gcm_key?

the operation seem want update

$db->apps->update(     array('_id' => $update['_id']),     array('$push' => array('keys.gcm_android' => $gcm_android)) ); 

but un-clear want end result be. produce following:

{     "_id" : objectid("532aa3d15fcd8ecb9ae23567"),     "id" : "dfk15ale12",     "keys" : {             "gcm_key" : "abc",             "app_secret" : "123",             "gcm_android" : [                     123             ]     } } 

assuming had value 123 in $gcm_android variable. if have array @ $pushall.

if looking add property keys use $set:

$db->apps->update(     array('_id' => $update['_id']),     array('set' => array('keys.gcm_android' => $gcm_android)) ); 

where result:

{     "_id" : objectid("532aa3d15fcd8ecb9ae23567"),     "id" : "dfk15ale12",     "keys" : {             "gcm_key" : "abc",             "app_secret" : "123",             "gcm_android" : 123     } }