The Create/Update Pattern

<?php
class Members extends Trongate {

    /**
     * Display a list of members.
     */
    public function manage(): void {
        $this->trongate_security->make_sure_allowed();

        $data = [
            'members' => $this->model->fetch_members(),
            'view_module' => 'members',
            'view_file' => 'manage'
        ];

        $this->templates->admin($data);
    }

    /**
     * Display the create or update member form.
     */
    public function create(): void {
        $this->trongate_security->make_sure_allowed();

        $update_id = segment(3, 'int');
        $submit = post('submit');

        // Load data from POST if creating new OR if validation failed
        // Otherwise load from database for editing
        if (($update_id === 0) || ($submit === 'Submit')) {
            $data = $this->model->get_data_from_post();
        } else {
            $data = $this->model->get_data_from_db($update_id);
        }

        $data['headline'] = ($update_id === 0) ? 'Create Member' : 'Update Member';
        $data['update_id'] = $update_id;
        $data['form_location'] = str_replace('/create', '/submit', current_url());
        $data['view_module'] = 'members';
        $data['view_file'] = 'create';

        $this->templates->admin($data);
    }

    /**
     * Handle form submission for creating or updating a member.
     */
    public function submit(): void {
        $this->trongate_security->make_sure_allowed();

        // Validate the submitted data
        $this->validation->set_rules('username', 'username', 'required|min_length[3]|max_length[30]');
        $this->validation->set_rules('email_address', 'email address', 'required|valid_email');

        $result = $this->validation->run();

        if ($result === true) {
            // Validation passed - save data and redirect
            $data = $this->model->get_data_from_post();
            $update_id = segment(3, 'int');

            if ($update_id === 0) {
                $this->db->insert($data, 'members');
                set_flashdata('The new member was successfully created.');
            } else {
                $this->db->update($update_id, $data, 'members');
                set_flashdata('The member was successfully updated.');
            }

            redirect('members/manage');
        } else {
            // Validation failed - redisplay form with errors
            $this->create();
        }
    }

    /**
     * Display the delete confirmation screen.
     */
    public function confirm_delete(): void {
        $this->trongate_security->make_sure_allowed();

        $update_id = segment(3, 'int');
        $this->model->get_data_from_db($update_id);

        $data = [
            'form_location' => str_replace('/confirm_delete', '/submit_confirm_delete', current_url()),
            'update_id' => $update_id,
            'view_module' => 'members',
            'view_file' => 'confirm_delete'
        ];

        $this->templates->admin($data);
    }

    /**
     * Handle confirmed deletion of a member.
     */
    public function submit_confirm_delete(): void {
        $this->trongate_security->make_sure_allowed();

        $update_id = (int) post('update_id', true);
        $this->db->delete($update_id, 'members');
        set_flashdata('The member record was successfully deleted.');
        redirect('members/manage');
    }
}

<?php
class Members_model extends Model {

    /**
     * Retrieve and sanitise member data from POST.
     * 
     * Used for both saving to database and redisplaying form after validation errors.
     * 
     * @return array
     */
    public function get_data_from_post(): array {
        $data = [
            'username' => post('username', true),
            'email_address' => post('email_address', true),
            'active' => (int) (bool) post('active', true)
        ];

        return $data;
    }

    /**
     * Retrieve a single member record from the database.
     * 
     * Used when editing an existing member.
     * 
     * @param int $update_id
     * @return array
     */
    public function get_data_from_db(int $update_id): array {
        $record_obj = $this->db->get_where($update_id, 'members');

        if ($record_obj === false) {
            http_response_code(404);
            echo 'Member not found';
            die();
        }

        $member = (array) $record_obj;
        return $member;
    }

    /**
     * Fetch all members and append a human-readable status.
     * 
     * @return array
     */
    public function fetch_members(): array {
        $members = $this->db->get('id', 'members');

        foreach ($members as $key => $member) {
            $active = (int) $member->active;
            $members[$key]->status = ($active === 1) ? 'active' : 'inactive';
        }

        return $members;
    }
}

<h1><?= $headline ?></h1>
<div class="card">
    <div class="card-heading">Member Details</div>
    <div class="card-body">
        <?php
        echo form_open($form_location, array('class' => 'highlight-errors'));
        
        echo form_label('Username');
        echo validation_errors('username');
        echo form_input('username', $username, array('placeholder' => 'Username...', 'autocomplete' => 'off'));

        echo form_label('Email Address');
        echo validation_errors('email_address');
        echo form_email('email_address', $email_address, array('placeholder' => '[email protected]'));

        echo '<label>';
        echo form_checkbox('active', 1, $active);
        echo ' Active member';
        echo '</label>';

        echo '<div class="text-center">';
        echo anchor('members/manage', 'Cancel', array('class' => 'button alt'));

        if ($update_id > 0) {
            echo anchor('members/confirm_delete/'.$update_id, 'Delete Member', array('class' => 'button danger'));
        }

        echo form_submit('submit', 'Submit');
        echo '</div>';

        echo form_close();
        ?>
    </div>
</div>

if (($update_id === 0) || ($submit === 'Submit')) {
    $data = $this->model->get_data_from_post();
} else {
    $data = $this->model->get_data_from_db($update_id);
}

public function get_data_from_post(): array {
    $data = [
        'username' => post('username', true),
        'email_address' => post('email_address', true),
        'active' => (int) (bool) post('active', true)  // 0 or 1
    ];
    return $data;
}