We can pass all form data using jquery on submit and get all value in codeigniter controller

Step:1

Create an HTML form with your input tag.

<form method="post" name="sub">
	<input type="text" name="name">
	<input type="text" name="email">
	<input type="text" name="mobile">
	<input type="file" name="userfile">
	<button type="submit">send</button>
</form>

Step:2

Create jquery function form submit and then after send all form value in codeigniter controller using ajax.

<script type="text/javascript">
$(document).ready(function (e){
$("#sub").on('submit',(function(e){
e.preventDefault();
$('#send').html('Please Wait <i class="fa fa-circle-o-notch fa-spin" style="font-size: 14px;"></i>');
$.ajax({
url: "<?php echo base_url(); ?>Post_ci/upload",
type: "POST",
data:  new FormData(this),
contentType: false,
cache: false,
processData:false,
success: function(data){
//$("#view").html(data);
},
error: function(){}
});

}));
});
</script>

Step:3 

Open your project Application/controller and create a controller class file and create a folder in site root uploads

<?php
class Post_ci extends CI_Controller
{
public function __construct()
{
parent::__construct();
$this->load->helper(array('form', 'url'));
$this->load->model('Post_model');
$this->load->library('image_lib');
}
	public function upload()
{
$config['upload_path']          = './uploads/'; // create folder in site root uploads
$config['allowed_types']        = 'gif|jpg|png';
$this->load->library('upload', $config);
if ( ! $this->upload->do_upload('userfile'))
{
	echo 'no image'
}

$data = array('upload_data' => $this->upload->data());
$img = $data['upload_data']['raw_name'];
$data = array(
'name' => $this->input->post('name'),
'email' => $this->input->post('email'),
'mobile' => $this->input->post('mobile'),
'img'=> $img
);
$query=$this->Post_model->post_data($data);

}// fun
}// class

	?>

Step:4

last step to create a model and submit all value in database.

	<?php
class Post_model extends CI_Model{
	public function __construct()
{
parent::__construct();
// Your own constructor code
$this->load->database();
}
public function post_data($data){
$this->db->insert('user', $data);
$insert_id = $this->db->insert_id();
return  $insert_id;
}
}
?>

Your database table where you submit all value.

CREATE TABLE IF NOT EXISTS `user` (
  `user_id` int(11) NOT NULL,
  `user_name` varchar(50) NOT NULL,
  `user_mobile` varchar(15) NOT NULL,
  `img` varchar(100) NOT NULL,
  `user_mail` varchar(50) NOT NULL
);