Laravel 4.2获得当月的记录

i got a problem in my project i am using Laravel 4.2.

Piece of code which have problem..

$xx = xx::where('user_id','=',$user_id)
            ->where('date','>=',$first_day) //$first_day is first day of any month
            ->where('date','<=',$last_day)//$last_day is last day of same month
            ->get();

print_r($xx);die(); 
//records present but empty array for current month but working fine for any previous month

Result

Illuminate\Database\Eloquent\Collection Object ( [items:protected] => Array ( ) )

Laravel last query log

Array ( [query] => select * from x_xx where user_id = ? and date = ? and date <= ? [bindings] => Array ( [0] => 17 [1] => 2016-04-1 [2] => 2016-04-30 ) [time] => 0.69 )

Running in mysql phpmyadmin i got 15 records

select * from x_xx where user_id = 17 and date >= '2016-04-1' and date <= '2016-04-30' //15 total records found in mysql