Ini gimana caranya ya ngebuat sistem posting berdasarkan user

gan ane bikin form posting nah ane bikin table postnya ada field namanya email_id mau ane join sama user id nah pas udh di posting gimana ya biar carany si field email_id dari table postfes ini otomatis keisi sama user id?

<h1 class="h3 mb-0 text-gray-800"><?= $title; ?></h1>
<?= $this->session->flashdata('message'); ?>
<div class="row">
    <div class="col-lg">
        <?php echo form_open_multipart('user/addpost'); ?>
        <div class="modal-body">
            <div class="form-group">
                <input type="text" class="form-control" id="namaFes" name="namaFes" placeholder="Nama Festival" value="<?= set_value('namaFes'); ?>">
            </div>
            <div class="form-group">
                <select name="daerah_id" id="daerah_id" class="form-control">
                    <option value="">Pilih Daerah</option>
                    <?php foreach ($nm_daerah as $nm) : ?>
                        <option value="<?= $nm['id_daerah']; ?>"><?= $nm['nm_daerah']; ?></option>
                    <?php endforeach; ?>
                </select>
            </div>
            <div class="form-group">
                <input type="text" class="form-control" id="tempat" name="tempat" placeholder="Tempat Pelaksanaan" value="<?= set_value('tempat'); ?>">
            </div>
            <label>Tanggal</label>
            <div class="form-group">
                <input type="date" class="form-control" id="tanggal" name="tanggal" placeholder="Tanggal Festival" value="<?= set_value('tanggal'); ?>">
            </div>

            <label> S/d </label>
            <div class="form-group">
                <p>Note : Isikan dengan tanggal yang sama jika 1 hari </p>
                <input type="date" class="form-control" id="tanggal2" name="tanggal2" placeholder="Tanggal Festival" value="<?= set_value('tanggal2'); ?>">
                <?= form_error('tanggal2', 'Isikan dengan tanggal yang sama jika acara tidak lebih dari satu hari ---', '<small class="text-danger pl-3">', '</small>'); ?>
            </div>
            <div class="form-group">
                <textarea style="height: 150px;" class="form-control" id="deskripsi" name="deskripsi" placeholder="Keterangan" value="<?= set_value('deskripsi'); ?>"></textarea>
            </div>
            <div class="form-group">
                <input type="text" class="form-control" id="email_id" name="email_id" value="<?= $_SESSION['email']; ?>" readonly>

                <!--<div class=" form-group">
                    <div class="form-check">
                        <input class="form-check-input" type="checkbox" value="1" name="isActive" id="isActive" checked>
                        <label class="form-check-label" for="isActive">
                            Is it active?
                        </label>
                    </div>
            </div>-->
                <div class="custom-file">
                    <input type="file" class="custom-file-input" id="image" name="image">
                    <label class="custom-file-label" for="image">Choose 1:1 image...</label>
                </div>
            </div>
            <div class="modal-footer">
                <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
                <button type="submit" class="btn btn-primary">Add</button>
                <? echo form_close(); ?>
            </div>
        </div>
    </div>
</div>
</div>
</div>
</div>

ini viewnya

public function addpost()
    {
        $data['title'] = 'Add Posting';
        $data['user'] = $this->db->get_where('user', ['email' => $this->session->userdata('email')])->row_array();

        $data['nm_daerah'] = $this->db->get('daerah')->result_array();
        $this->load->model('PostModel', 'post');
        $data['postfes'] = $this->post->getPostModel4();

        $this->form_validation->set_rules('namaFes', 'Nama Festival', 'required|trim');
        $this->form_validation->set_rules('daerah_id', 'Nama Daerah', 'required|trim');
        $this->form_validation->set_rules('tanggal', 'Tanggal', 'required|trim');
        $this->form_validation->set_rules('tanggal2', 'Tanggal', 'required|trim');
        $this->form_validation->set_rules('deskripsi', 'Deskripsi', 'required|trim');
        $this->form_validation->set_rules('tempat', 'Deskripsi', 'required|trim');

        if ($this->form_validation->run() == false) {

            $this->load->view('templates/user-header', $data);
            $this->load->view('templates/user-sidebar', $data);
            $this->load->view('templates/user-topbar', $data);
            $this->load->view('user/addpost', $data);
            $this->load->view('templates/user-footer');
        } else {

            $namaFes = $this->input->post('namaFes');
            $daerah = $this->input->post('daerah_id');
            $tempat = $this->input->post('tempat');
            $tanggal = $this->input->post('tanggal');
            $tanggal2 = $this->input->post('tanggal2');
            $desk = $this->input->post('deskripsi');
            $idpost = $this->input->post('email_id');
            $image = $_FILES['image'];
            if ($image = '') {
            } else {
                $config['upload_path'] = './assets/img/posting/';
                $config['allowed_types'] = 'jpg|gif|png|jpeg';

                $this->load->library('upload', $config);
                if (!$this->upload->do_upload('image')) {
                    echo 'failed upload image';
                    die();
                } else {
                    $image = $this->upload->data('file_name');
                }
            }

            $data = [
                'namaFes' => $namaFes,
                'daerah_id' => $daerah,
                'tempat' => $daerah,
                'tanggal' => $tanggal,
                'tanggal2' => $tanggal2,
                'deskripsi' => $desk,
                'email_id' => $idpost,
                'image' => $image
            ];

            $this->db->insert('postfes', $data);
            $this->session->set_flashdata('message', '<div class="alert alert-success" role="alert">Please wait admin approve your post</div>');
            redirect('user/addpost');
        }
    }

ini controllernya

public function getPostModel4()
    {

        $query = "SELECT `postfes`.*, `user`.`id`
        FROM `postfes` JOIN `user`
        ON `postfes`.`email_id` = `user`.`id`
        WHERE `postfes`.`email_id` = '" . $_SESSION['id'] . "'";

        return $this->db->query($query)->result_array();
    }

ini modelnya mohon bantuannya gan