Cannot upload csv file using codeigniter - php

Question

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?