controller.php

public function signup() {
    $data['title'] = 'Signup';
    $this->load->helper('form');
    $this->load->library('form_validation');
    $this->load->model('user_model');

    $this->form_validation->set_rules('firstname', 'First name', 'required');
    $this->form_validation->set_rules('lastname', 'Last name', 'required');
    $this->form_validation->set_rules('email', 'Email', 'required|valid_email');
    $this->form_validation->set_rules('password', 'Password', 'required');
    
    if ($this->form_validation->run() === FALSE) {

        $this->load->view('templates/header', $data);
        $this->load->view('user/signup', $data);
        $this->load->view('templates/footer');
    } else {
        $this->user_model->createUser();
        $this->load->view('templates/header', $data);
        $this->load->view('user/usercreated');
        $this->load->view('templates/footer');
    }
}

model.php

public function createUser() {
    try {
        $data = array(
            'first_name' => $this->input->post('firstname'),
            'last_name' => $this->input->post('lastname'),
            'email' => $this->input->post('email'),
            'gender' => $this->input->post('gender'),
            'birthday' => $this->input->post('birthday'),
            'bio' => $this->input->post('aboutme'),
            'password' => $this->input->post('password')
        );

        $data['salt'] = $this->saltCreate($data['email']);
        $data['password'] = $this->passwordHash($data['password'], $data['salt']);
    } catch (Exception $e) {
        echo $e->getMessage();
    }
}

view.php

<div data-role="content">
    <?php echo validation_errors(); ?>
    <?php echo form_open('user/signup', array('data-ajax' => 'false')) ?>
    Input fiels with * are mandatory!
    <div data-role="fieldcontain">
        <fieldset data-role="controlgroup" data-mini="true">
            <label for="firstname">
                First name *
            </label>
            <input name="firstname" id="firstname" placeholder="" value="test-<?php echo rand(); ?>" type="text">
        </fieldset>
    </div>
    <div data-role="fieldcontain">
        <fieldset data-role="controlgroup" data-mini="true">
            <label for="lastname">
                Last name *
            </label>
            <input name="lastname" id="lastname" placeholder="" value="test-<?php echo rand(); ?>" type="text">
        </fieldset>
    </div>
    <div data-role="fieldcontain">
        <fieldset data-role="controlgroup" data-mini="true">
            <label for="email">
                Email * (is your log in)
            </label>
            <input name="email" id="email" placeholder="" value="test-<?php echo rand(); ?>@test.de" type="email">
        </fieldset>
    </div>
    <div data-role="fieldcontain">
        <fieldset data-role="controlgroup" data-mini="true">
            <label for="password">
                Password *
            </label>
            <input name="password" id="password" placeholder="" value="test-<?php echo rand(); ?>" type="password">
        </fieldset>
    </div>
    <div data-role="fieldcontain">
        <fieldset data-role="controlgroup" data-mini="true">
            <label for="birthday">
                Birthday
            </label>
            <input name="birthday" id="birthday" placeholder="" value="" type="date">
        </fieldset>
    </div>
    <div data-role="fieldcontain">
        <label for="gender">
            Gender
        </label>
        <select id="gender" name="gender" data-mini="true">
            <option value="male">Male</option>
            <option value="female">Female</option>
        </select>
    </div>
    <div data-role="fieldcontain">
        <fieldset data-role="controlgroup">
            <label for="aboutme">
                About me
            </label>
            <textarea name="aboutme" id="aboutme" placeholder="" data-mini="true"></textarea>
        </fieldset>
    </div>
    <div class="ui-block-b">
        <button type="submit" data-theme="a" class="ui-btn-hidden" aria-disabled="false" data-mini="true">Submit</button>
    </div>
    </form>
</div>