Show all model validation errors on top of the page in cakePHP

You can get all validation errors from the $this->validationErrors variable on the view. Then feel free to iterate through them and display as you like. They will be organized by model, like so:

array(
  'User' => array(
    'username' => 'This field cannot be empty.',
    'password' => 'This field cannot be empty.'
  )
);

Then you can iterate through them on the view and display them as such. This example displays them as an unordered list:

$errors = '';
foreach ($this->validationErrors['User'] as $validationError) {
  $errors .= $this->Html->tag('li', $validationError);
}
echo $this->Html->tag('ul', $errors);

Lastly, you can hide the form helper's automatic error messages by hiding them with CSS or setting the FormHelper defaults to not show them.

CSS

.input.error {
  display: none;
}

or

in the view

$this->Form->inputDefaults(array(
  'error' => false
));