I have following datatable:

var dataTable = $('#dataTable').DataTable({

    "processing": true,
    "serverSide": true,
    "order": [],
    "ajax": {
        url: "<?php echo base_url() . 'crud/fetch_patient'; ?>",
        type: "POST",
    },
    "columnDefs": [{
        targets: 2,
        render: DataTable.render.datetime('DD.MM.YYYY'),
        type: 'datetime-moment'
    }, {
        targets: 7,
        "orderable": false,
    }, ],
});

First column is last name, second column is first name. I would like to search lastname (column 0) and first name (column 1) with space after lastname in datatable searchbox. Example "Doe John". When I write Doe and space ('Doe ') in searchbox my datatable is empty. Here is what I tried:

"ajax": {
    url: "<?php echo base_url() . 'crud/fetch_patient'; ?>",
    type: "POST",
    data: function(d) {
        d.search_terms = $('#dataTable_filter input').val().trim().split(' ');
    },
    success: function(data) {
        console.log(data);
    }
},

Codeigniter - controller

function fetch_patient()
     {
          $this->load->model("crud_model");
          $u_id = $this->session->userdata('u_id');
          $fetch_data = $this->crud_model->make_datatables($u_id);
          $data = array();
          foreach ($fetch_data as $row) {
               $sub_array = array();
               $sub_array[] = $row->pr_lname;
               $sub_array[] = $row->pr_fname;
               $sub_array[] = $row->pr_bdate;
               $sub_array[] = date_diff(date_create($row->pr_bdate), date_create('now'))->y;
               $sub_array[] = mb_strlen($row->pr_number) == 9 ? preg_replace("/(\\w{3})/uim", "$1 ", $row->pr_number) : $row->pr_number;
               $sub_array[] = $row->pr_diseases != '' ? 'Tak' : 'Nie';
               $sub_array[] = $row->pr_date;
               $sub_array[] = '<a class="btn btn-brown p_tb_03" href="' . base_url() . 'maincontrol/edit_form/' . $row->pr_id . '">Edytuj</a><a class="btn btn-green ml_5 p_tb_03" href="' . base_url() . 'maincontrol/patientdataview/' . $row->pr_id . '">Przeglądaj</a><a class="btn btn-medium-dark ml_5 p_tb_03" href="' . base_url() . 'maincontrol/xraysview/' . $row->pr_id . '#xrays' . '">RTG</a><a class="btn btn-blue ml_5 p_tb_03" href="' . base_url() . 'maincontrol/add_findings/' . $row->pr_id . '#findings' . '"><i class="fa fa-plus"></i> Zabieg</a><a class="btn btn-medium-dark ml_5 p_tb_03" href="' . base_url() . 'maincontrol/add_xrays/' . $row->pr_id . '#xrays' . '"><i class="fa fa-plus"></i> RTG</a>';

               $data[] = $sub_array;
          }
          $output = array(
               "draw" => intval($_POST["draw"]),
               "recordsTotal" => $this->crud_model->get_all_data($u_id),
               "recordsFiltered" => $this->crud_model->get_filtered_data($u_id),
               "data" => $data
          );
          echo json_encode($output);
     }

Codeigniter - model

var $table = "patient_record";
     var $select_column = array("pr_id", "pr_lname", "pr_fname", "pr_bdate", "pr_bdate", "pr_number", "pr_diseases", "pr_date");
     var $order_column = array("pr_lname", "pr_fname", "pr_bdate", "pr_bdate", "pr_number", "pr_diseases", "pr_date");

     function make_datatables($pr_user_id)
     {
          $this->db->select($this->select_column);
          $this->db->from($this->table);
          $this->db->where('pr_user_id', $pr_user_id);

          if (isset($_POST["search"]["value"])) {
               $this->db->group_start(); 
               $this->db->like("pr_date", $_POST["search"]["value"]);
               $this->db->or_like("pr_lname", $_POST["search"]["value"]);
               $this->db->or_like("pr_fname", $_POST["search"]["value"]);
               $this->db->or_like("pr_bdate", $_POST["search"]["value"]);
               $this->db->or_like("pr_number", $_POST["search"]["value"]);
               $this->db->or_like("pr_diseases", $_POST["search"]["value"]);
               $this->db->group_end();
          }
          if (isset($_POST["order"])) {
               $this->db->order_by($this->order_column[$_POST['order']['0']['column']], $_POST['order']['0']['dir']);
          }
          if ($_POST["length"] != -1) {
               $this->db->limit($_POST['length'], $_POST['start']);
          }
          $query = $this->db->get();
          return $query->result();
     }
     function get_filtered_data($pr_user_id)
     {
          $this->db->select($this->select_column);
          $this->db->from($this->table);
          $this->db->where('pr_user_id', $pr_user_id);
          if (isset($_POST["search"]["value"])) {
               $this->db->group_start(); 
               $this->db->like("pr_date", $_POST["search"]["value"]);
               $this->db->or_like("pr_lname", $_POST["search"]["value"]);
               $this->db->or_like("pr_fname", $_POST["search"]["value"]);
               $this->db->or_like("pr_bdate", $_POST["search"]["value"]);
               $this->db->or_like("pr_number", $_POST["search"]["value"]);
               $this->db->or_like("pr_diseases", $_POST["search"]["value"]);
               $this->db->group_end();
          }
          if (isset($_POST["order"])) {
               $this->db->order_by($this->order_column[$_POST['order']['0']['column']], $_POST['order']['0']['dir']);
          }
          $query = $this->db->get();
          return $query->num_rows();
     }
     function get_all_data($pr_user_id)
     {
          $this->db->select("pr_date, pr_lname, pr_fname, pr_bdate, pr_number, pr_diseases");
          $this->db->from($this->table);
          $this->db->where('pr_user_id', $pr_user_id);

          return $this->db->count_all_results();
     }

This code shows me an empty array in console when I write 'Doe John'. Could you help me please? Thanks in advance.