function upload()
    {
        $request = 1;
        if (isset($_POST['request'])) {
            $request = $_POST['request'];
        }

        //upload
        if ($request == 1) {
            $msg = "";
            if (!empty($_FILES['file']['name'])) {
                $cpt = count($_FILES['file']['name']);
                $config['upload_path'] = './assets/images/slider';
                $config['allowed_types'] = 'jpeg|jpg|png|gif';
                $config['max_size']      = '0';
                $config['overwrite']     = true;
                $config['width']    = 700;
                $config['height'] = 700;
                $config['file_name'] = $_FILES['file']['name'];

                //load upload
                $this->load->library('upload', $config);

                if ($this->upload->do_upload('file')) {
                    $uploadData[] = $this->upload->data();
                    for ($i = 0; $i < $cpt; $i++) {
                        $data['lokasi_gambar'] = base_url() . "assets/images/slider/" . $uploadData[$i]['file_name'];
                        // $this->SERVER_API->_postAPI('slider/', $data, $this->token);
                    }
                    $msg = "SUKSES";
                } else {
                    $msg = "GAGAL";
                }
            }
            echo $msg;
        }

        //remove
        if ($request == 2) {
            $filename =  './assets/images/slider/' . $_POST['name'];
            unlink($filename);
            exit;
        }
    }
	
	
	<script>
    $(document).ready(function() {
        // Multiple files upload
        $("#dropzone_multiple").dropzone({
            paramName: "file", // The name that will be used to transfer the file
            dictDefaultMessage: 'Drop files to upload <span>or CLICK</span>',
            addRemoveLinks: true,
            removedfile: function(file) {
                var name = file.name;

                $.ajax({
                    type: 'post',
                    url: '<?= base_url('Slider/upload') ?>',
                    data: {
                        name: name,
                        request: 2
                    },
                    success: function(response) {
                        console.log(response);
                    }
                });
                var _ref;
                return (_ref = file.previewElement) != null ? _ref.parentNode.removeChild(file.previewElement) : void 0;
            }
        });
    })
</script>