[Solved] When Insert New User Get 2 preg_match() errors

[eluser]riwakawd[/eluser]
I don't know why I am getting 2 errors some array issue which I am not sure of does not give the error on register model on codeigniter?

Error 1
A PHP Error was encountered
Severity: Warning
Message: preg_match() expects parameter 2 to be string, array given
Filename: mysql/mysql_driver.php
Line Number: 199

Error 2
A PHP Error was encountered
Severity: Warning
Message: preg_match() expects parameter 2 to be string, array given
Filename: database/DB_driver.php
Line Number: 622

Code:

public function insert_user() {

    $sql = array(
     'firstname' => $this->input->post('firstname'),
     'ip' => $this->session->userdata('ip_address'),
     'lastname' => $this->input->post('lastname'),
     'email' => $this->input->post('email'),
     'country' => $this->input->post('country'),
     'username' => $this->input->post('username'),
     'password' => $this->input->post('password')
  );

  $this->db->insert('users', $sql);

  $result  = $this->db->query($sql);

  if ($this->db->affected_rows() === 1) {
   return 'firstname';
  } else {
   $this->load->library('email');
   $this->email->from('[email protected]', "From Website Admin");
   $this->email->to('[email protected]');
   $this->email->subject('Problem Inserting User Into Database');

   if(isset($email)) {
    $this->email->message('Unable To Register And Insert User With Email Of' .$email . 'To The Database');
   } else {
    $this->email->message('Unable To Register And Insert User To The Database');
   }

   $this->email->send();
   return false;
  }

   }