CakePHPでユーザー新規登録時にメールを送りたいです。

CakePHPでユーザーが新規登録フォームに情報を入力後に本登録メールを送りたいのですが、メールを送るための関数（activate)がうまく機能しません。
また、この関数をコメントアウトするとユーザーの情報がうまくDBに登録されるのですが、コメントアウトを外すと
「Error: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'Array' in 'field list'」と言うエラーが出てしまいます。
activate関数に関して修正していただけると幸いです。

<?php
 App::uses('AppController','Controller');
 App::uses('CakeEmail','Network/Email');


    class UsersController extends AppController {
        public $scaffold;
        public $helpers = array('Html','Form','Flash');
        public $name = 'User';  
        public $users = array('User','profile');    
        public $presetVars = true;
        public $components = array('Search.Prg');

        //public $components = array('Auth');
        //public function beforeFilter()
        //{
        //$this->Auth->allow('signup');
        //}

        public function signup()
        {
            if($this->request->is('post'))
        {
            // die(pr($this->request->data));
            if(is_uploaded_file($this->request->data['User']['profile_Image']['tmp_name']))
            {
                $fileNameFull = $this->request->data['User']['username'] . "_" . $this->request->data['User']['profile_Image']['name'];
                $oldFile = '../../app/webroot/img/'.$fileNameFull; 

                move_uploaded_file(
                    $this->request->data['User']['profile_Image']['tmp_name'],
                    $oldFile
                );
                $this->User->create();
                $this->request->data['User']['profile_Image'] = $fileNameFull;
                if ($this->User->save($this->request->data)) {
                    $this->Session->setFlash('Registration suceessful');
                }else{
                    $this->Session->setFlash('Error');
                }
            }



            if($this->User->save($this->data))
        {
                    $url='activate/'.$this->User->id.'/'.$this->AppModel->getActiviationHash();
                    $url=Router::url($url,true);

                      $email=new CakeEmail();
                      $email->from(array('KD******@gmail.com' =>'Sender'));
                      $email->to($this->data['User']['email']);
                      $email->subject('Registration mail');
                      $email->send($url);

                $this->Session->setFlash('Registration suceessful');
               }else{
                $this->Session->setFlash('Error');
            }
          }
         }

        public function activate($user_id=null,$in_hash=null)
        {
            $this->User->id=$user_id;
            if($this->User->exists() && $in_hash==$this->User->getActiviationHash()){
               $this->User->saveFiled('active',1);
            $this->Session->setFlash('Your registration is seccessed');
        }else{
            $this->Session->setFlash('Invalid link');
        }
        }

        public function login()
        {
            if ($this->request->is('post'))
            {
                if ($this->Auth->login()) {
                    return $this->redirect($this->Auth->redirectUrl());
            }
                $this->Flash->error(__('Invalid username or password, try again'));
            }

        }


        public function logout()
        {     
        return $this->redirect($this->Auth->logout());
        }

        public function search()
        {
        $this->post->recursive = 0;
        $this->Prg->commonProcess();
        $this->paginate = array('conditions' => $this->Post->parseCriteria($this->passedArgs),);
        //pr($this->paginate());//debug
        $this->set('posts', $this->paginate());
         }


        public function find()  
        {
        // $user=$this->_connect_model->get('User')->getUserRecord($user['username']);      
        // $statuses=$this->_connect_model->get('Status')->getPostMessage($user['id']);///////postとる

         $followState=null;//////////////////////サインイン中のユーザーじゃない
         if($this->_session->isAuthenticated()){
             $loginUser=$this->_session->get('user_id');
         //}/////////$loginUser=サインインしているユーザー　
          ////////$user=フォローするユーザーのID
         if($this->session->isAuthenticated($following_id)){
             if($loginUser['id']!==$user['id']){
                    $state=$this->Follow->get('following_id')////////
                    ->isFollowedUser($my['id'],$user['id']);/////////フォロー済みか確認
               }
            }
              $user_view = $this->render(array(
                  'user'=>$user,
                  'statuses'=>$statuses,
                  'followstate'=>$followstate,
                  '_token'=>$this->getToken(self::FOLLOW),
            ));

            return $user_view;
            $this->set('statuses',$statuses);

         $userNameKeyword=$this->request->data['Users']['username'];
         $users=$this->User->find('all', [
                 'conditions' => [
                 'User.username LIKE' => '%'.$userNameKeyword.'%'
            ],
        ]);
        $this->set('users',$users);
        $this->render();
     }