CheckData

 public function checkdata() {
        $nik    = $this->input->post('nik', 'true'); // Ambil data NIK yang dikirim lewat AJAX

        $this->db->select('p.*, k.kecamatan_nama, d.desa_nama');
        $this->db->from('rtlh_penduduk_jepara p');
        $this->db->join('rtlh_kecamatan k', 'p.kecamatan_id = k.kecamatan_id');
        $this->db->join('rtlh_desa d', 'p.desa_id = d.desa_id');
        $this->db->where('p.penduduk_nik', $nik);

        $query  = $this->db->get();
        $row    = $query->result();

        if(count($row) > 0) {
            $data = $query->row();

            $callback = array(
                'status'        => 'success',
                'nama'          => trim($data->penduduk_nama)
            );
        } else {
            $callback = array('status' => 'failed'); // set array status dengan failed
        }

        echo json_encode($callback); // konversi varibael $callback menjadi JSON
    }