php - Catchable fatal error: Object of class mysqli could not be converted to string -

i trying create registration form project unfortunately got error while not find error in code!please me ride issue !

my code

<?php  // file connected regform.php     $firstname= $_post['firstname'];     $lastname =$_post['lastname'];     $email =$_post['email'];     $password =$_post['password'];     $confirmpassword =$_post['confirmpassword'];     $address =$_post['address'];     $balance =$_post['balance'];     $password_hash = md5($password);  $bookconn = mysqli_connect("localhost", "root","", "bookstore") or die("wrong execution");      $querys = "select email customer";     $resultsq = mysqli_query($bookconn , $querys);     $flag=0;  while($row=mysqli_fetch_array($resultsq)) {     if($email == $row['email'])     {         $flag=1;     } }      if($flag==0)     {             if($password == $confirmpassword)          {             $query = "insert  user (firstname , lastname ,email , password , address , balance )values('".$firstname."', '".$lastname."' ,'".$email."' , '".$password_hash."', '".$address."' , '".$balance."')";             $result = mysqli_query($bookconn , $query) or die($bookconn);               if ($result)                 {                     echo "successfuly registered";                 }              else {                     echo "something went wrong!";                  }         }          else{             echo "passowrd not match!";             }     }  else{          echo "email existed in database!";      } mysqli_close($dbc); ?> 

there 2 error seems in code:-

1. mysqli_close($dbc). never created $dbc in code. must mysqli_close($bookconn).

2. you need modified last mysqli_query this:-

   $result = mysqli_query($bookconn , $query) or die(mysqli_error($bookconn));

note:- hope doing these changes rid of proble. thanks.