php - Active records query is not working with a set of values which works for normal insert/update -

I am using CI and for using something in DB, I am using active record method.

  $ this-> User- & gt; Insert ($ input);  

is not working, where $ input is below.

  array (8) {["user_type"] => String (1) "7" ["first_name"] = & gt; String (6) "Manojza" ["last_name"] = & gt; String (5) "hippo" ["mobile"] = & gt; String (15) "+ 91 94456594456" ["country"] = & gt; String (2) "IN" ["state"] = & gt; String (4) "1923" ["city"] = & gt; String (7) "Bijapur"}  

But if the query is $ this-> Db , then it is working. I've confirmed that the 'user' model ( class user has extended the mimodel ) has extended 'MY_Model'.

  $ this-> Db- & gt; Insert ('user', $ input);  

The query works.

What could be the problem? help please.