无法弄清楚我的函数注册验证（）有什么问题？

Question

我无法弄清楚我的代码有什么问题。它在这个函数中有问题，因为当我点击登录时的提交按钮时，页面是完全白色的，网址是http://localhost:8888/TESTING/PHP/HELLER-RECIPES/login/signup_validation

如果有人能帮我弄清楚我做错了什么，我会非常满意。

这是我的功能：

public function signup_validation(){
        $this->load->library('form_validation');
        $this->form_validation->set_rules('email','Email', 'required|trim|valid_email|is_unique[users.email]');
        $this->form_validation->set_rules('password','Password', 'required|trim');
        $this->form_validation->set_rules('cpassword','Confirm Password', 'required|trim|matches[password]');

        $this->form_validation->set_message('is_unique', 'That email address already exist.');

        if($this->form_validation->run()){
            $key = md5(uniqid());
            $this->load->library('email', array('mailtype'=>'html'));
            $this->load->model('model_users');
            $this->email->from('theller5567@gmail.com', 'Travis');
            $this->email->to($this->input->post('email'));
            $this->email->subject("confirm your account");

            $message = "<h1>Thank you for signing up!</h1>";
            $message.= "<p><a href='".base_url()."login/register_user/$key'>Click here</a> to confirm your account.</p>";
            $this->email->message($message);

            if($this->model_users->add_temp_user($key)){
            //Send a email to the user
            if($this->email->send()){
                echo "The email has been sent";
            } else echo "Could not send the email";
        } else echo "Problem adding to database";
        } else {
            $this->load->view('includes/header');
            $this->load->view('includes/navigation-header');
            $this->load->view('signup');
            $this->load->view('includes/bottom-nav');
            $this->load->view('includes/footer');
        }
    }

我最好的猜测是这个问题存在于此部分：

if($this->model_users->add_temp_user($key)){
            //Send a email to the user
            if($this->email->send()){
                echo "The email has been sent";
            } else echo "Could not send the email";
        } else echo "Problem adding to database";
    } else {

我相信这个原因我没有遇到问题，直到我弄乱了代码的这一部分，如果我删除了这一部分我再也不会得到错误。