To perform add, delete, edit operation in Cake-PHP, first you need to create database table to store records.

CREATE TABLE `users` (
  `id` int(10) UNSIGNED NOT NULL,
  `username` varchar(128) DEFAULT NULL,
  `password` varchar(128) DEFAULT NULL,
  `email` varchar(128) DEFAULT NULL,
) 

Examples of CakePHP's Add, Edit, Delete action.

Add Function: add() function is used to save data using the model (Suppose model name-> USER). If the request method is HTTP then delete action perform right task otherwise it will give error.

public function add() 
    {
      if ($this->request->is('post')) 
        {
            $this->User->create();
            if ($this->User->save($this->request->data)) 
            {
                $this->Session->setFlash(('The user has been saved.'));
                        return $this->redirect(array('controller' => 'Users', 'action' => 'index'));
            } else 
            {
                $this->Session->setFlash(('The user could not be saved. Please, try again.'));
            }
        }
}

Edit Function: In edit(), first user have to pass $id parameter to access an existing record. if the ID have't pass or user does nor exit then, it will give an error.

public function edit($id = null) {
        if (!$this->User->exists($id)) {
            throw new NotFoundException(_('Invalid user'));
        }
        if ($this->request->is(array('post', 'put'))) {
            if ($this->User->save($this->request->data)) {
                $this->Session->setFlash(('The user has been saved.'));
                return $this->redirect(array('action' => 'index'));
            } else {
                $this->Session->setFlash(('The user could not be saved. Please, try again.'));
            }
        } else {
            $options = array('conditions' => array('User.' . $this->User->primaryKey => $id));
            $this->request->data = $this->User->find('first', $options);
        }
    }

Delete Function: delete() function deletes the data which is specified by ID. After deleting the data, user would be redirected to index page.

public function delete($id = null) {
        $this->User->id = $id;
        if (!$this->User->exists()) {
            throw new NotFoundException(('Invalid user'));
        }
        $this->request->allowMethod('post', 'delete');
        if ($this->User->delete()) {
            $this->Session->setFlash(('The user has been deleted.'));
        } else {
            $this->Session->setFlash(('The user could not be deleted. Please, try again.'));
        }
        return $this->redirect(array('action' => 'index'));
    }

Index Function: indiex() action is used to fetch data from DB & showing it in front end using index.ctp file.

public function index()
        {
            $users = $this->User->find('all');
            $this->set('users', $users);
         }

Now create a view files (add,edit,index) for presentation under app\View\users(add.ctp, edit.ctp,index.ctp)

index.ctp:

            <?php echo $this->Html->link('Edit', array('action' => 'edit', $user['User']['id'])); ?>
            <?php echo $this->Form->postLink('Delete', array('action' => 'delete', $user['User']['id'])),
        </td>
    </tr>
<?php endforeach; ?>
    </tbody>

    </table>

<?php echo $this->Form->create('User'); ?>
    <?php echo ('Edit User'); ?>
    <?php
        echo $this->Form->input('id');
        echo $this->Form->input('username');
        echo $this->Form->input('password');
        ?>
    </fieldset>
<?php echo $this->Form->end(__('Submit')); ?>

<?php echo $this->Form->create('User'); ?>
    <?php echo __('Add User'); ?>

        echo $this->Form->input('username');
        echo $this->Form->input('password');
        echo $this->Form->input('email');
    ?>
<?php echo $this->Form->end(__('Submit')); ?>