Codeigniter CSRF valid for only one time ajax request

In my opinion you should try to recreate your csrf token each request

Try this code example...

For the js funcion

var csrfName = '<?php echo $this->security->get_csrf_token_name(); ?>',
    csrfHash = '<?php echo $this->security->get_csrf_hash(); ?>';
("#avatar").change(function(){
    var link = $("#avatar").val();

    var dataJson = { [csrfName]: csrfHash, id: "hello", link: link };

    $.ajax({
        url : "<?php echo base_url('main/test'); ?>",
        type: 'post',
        data: dataJson,            
        success : function(data)
        {   
            csrfName = data.csrfName;
            csrfHash = data.csrfHash;
            alert(data.message);
        }  
    });
});

and for the controller

public function test() { 
    $config['upload_path'] = './uploads/'; 
    $config['allowed_types'] = 'gif|jpg|png'; 
    $config['max_size'] = 500; 
    $config['max_width'] = 260; 
    $config['max_height'] = 260; 

    $reponse = array(
                'csrfName' => $this->security->get_csrf_token_name(),
                'csrfHash' => $this->security->get_csrf_hash()
                )

    $this->load->library('upload', $config); 
    if (!$this->upload->do_upload('link')) { 
        $reponse['message'] = "error"; 
    } 
    else { 
        $data = array('upload_data' => $this->upload->data()); 
        $image_name = $data['upload_data']['file_name']; 
        $reponse['message'] = $image_name; 
    } 

    echo json_encode($reponse);
}

Let me know and good luck

Note: When someone ask you for posting more data to the question, don't post it as a comment or answer, it's better to edit the question itself and adding the stuff

Try this -> In your test.php file, give the action attribute as

action="<?php echo site_url();?>/static_data/test_add"

Then, in your practice.js file:

$('#test_form').submit(function() {
var tdata= $("#test_form").serializeArray();
var that = $(this),
url = that.attr('action'),
type = that.attr('method'),
data = tdata;

Now, for testing, in your success function in practice.js, just write the following:

success: function(response) {
         console.log(response);
}

Here, the response you get is what your controller returns to you, now to test that, just type echo "hello"; or anything, just echo out something. (This is because you said teach me :) )

Now to see if this is working, open deveoper tools (if you are in google chrome), go to the console tab and then from bottom, select log, if everything is fine, it will return your echoed message written in your controller.

Also, to see if the form is submitted correctly, select the network tab, when you hit the submit button, the network tab will show you if the data has been submitted correctly or not.

Try this, if doesn't work, leave a comment.

i think your problem may be in ajax code since you are using formData object . try append the message variable with it

$('#submit').on('click', function(){

  var fd = new FormData(this);
  fd.append('file',$('#file')[0].files[0]);
  fd.append('message ',$('#message').val());

  $.ajax({
    method:"POST",
    url:"<?php echo site_url('home/send_chat');?>",    
    data: fd,  
    cache: false,
    contentType: false,
    processData: false,   
    success: function(data){                 
      alert(data);
    },
    error: function(xhr, status, error) {
      alert(xhr.responseText);
    }  
  });
});