Codeigniter 2.x表单验证错误，没有验证错误

Question

我正在尝试验证表单，但验证始终返回false，validation_errors()返回空字符串。我无法理解这段代码有什么问题：

function submission_register_form(){


    if (!$this->input->is_ajax_request()) { exit('no valid req.'); }

        $FormRules = array(
            array(
                'field' => 'email',
                'label' => 'Email Address',
                'rules' => 'required|valid_email|xss_clean|callback_email_check'
            ),
            array(
                'field' => 'password1',
                'label' => 'Password',
                'rules' => 'required|min_length[4]|xss_clean'
            ),
        );
        $this->form_validation->set_rules($FormRules);



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

            $email = $this->input->post('email');
            $username = $email;
            $password = $this->input->post('password1');


            if ($this->ion_auth->register($username, $password, $email, $meta,NULL) == TRUE) {

                echo '<div class="success">Thank you for registering. To activate your account, please click on the link in the activation message which has been sent to your e-mail address.</div>';

            } else {

                echo '<div class="success">Registration did not complete. Please contact the site administrator.</div>';
            }

        }
        else {
            echo '<div class="errors">'.validation_errors().'</div>';
        }

}

这是我的html表单：

    <div class="login-form">
        <a href="/auth/login" class="signup">Log In <img src="<?php echo base_url('images/right-arrow-red.png')?>" alt="" /></a>
        <h2>Create an Account</h2>
        <p>Howday! Welcome!</p>
        <div class="jsError"></div>
        <?php echo form_open('auth/submission_register_form', array('class'=>'signupjsform')); ?>
            <div class="input">
                <label for="email">EMAIL ADDRESS</label>
                <input type="text" id="email" name="email" placeholder="example@site.com" />
            </div>

            <div class="input">
                <label for="password">PASSWORD</label>
                <input type="password" id="password" name="password1" placeholder="your password" />
            </div>
            <div class="check_forgot fix">
                <p>By Signing up, you agree with our <a href="#">Terms of Service</a> and <a href="#">Privacy Statement</a>.</p>
            </div>
            <div class="submit">
                <p><input type="submit" value="SIGN IN" /> <span>OR</span> <a href="#"><img src="<?php echo base_url('images/facebook-icon.png')?>" alt="" /> SIGN UP WITH FACEBOOK</a></p>
            </div>
        <?php echo form_close(); ?>
    </div>

  <script type="text/javascript">
       $(document).ready(function(){
         $('form.signupjsform').on('submit', function(form){
        form.preventDefault();
        $.post('/index.php/auth/submission_register_form', $('form.jsform').serialize(), function(data){
            alert(data);
            $('div.jsError').html(data);
        });
    });
});