Cannot upload csv file using codeigniter

I try to import my.csv file but I cannot upload file and find out my problem. No error show, if I print my code see all empty value don't show anything.

Here is my code:

public function load_data(){
    $result = $this->web->select();
//  print_r($result);exit;
      $output = '
       <h3 align="center">Imported User Details from CSV File</h3>
            <div class="table-responsive">
             <table class="table table-bordered table-striped">
              <tr>
               <th>Sr. No</th>
               <th>First Name</th>
               <th>Last Name</th>
               <th>Phone</th>
               <th>Email Address</th>
              </tr>
      ';
      $count = 0;
      if($result->num_rows() > 0)
      {
       foreach($result->result() as $row)
       {
        $count = $count + 1;
        $output .= '
        <tr>
         <td>'.$count.'</td>
         <td>'.$row->first_name.'</td>
         <td>'.$row->last_name.'</td>
         <td>'.$row->phone.'</td>
         <td>'.$row->email.'</td>
        </tr>
        ';
       }
      }
      else
      {
       $output .= '
       <tr>
           <td colspan="5" align="center">Data not Available</td>
          </tr>
       ';
      }
      $output .= '</table></div>';
      echo $output;
}


 public function import() {
    $file_data = $this->csvimport->get_array($_FILES["csv_file"]["tmp_name"]);
   foreach($file_data as $row){
     $data[] = array(
      'first_name' => $row["First Name"],
      'last_name'  => $row["Last Name"],
      'phone'   => $row["Phone"],
      'email'   => $row["Email"]
     );
  }
  $this->web->insert($data);
 }

How can I upload csv and xlsx file by using codeigniter in easy and simple way?