How to throw errors in PHP using an MVC Architecture

I am trying to re-architect a web application I developed to use the MVC pattern, but I'm not sure how to handle errors. For example:

class AM_Products extends AM_Object 
{
    public function save( $new_data = array() ) 
    {
        // Validate input

        // Save input
  开发者_C百科  }
}

If I pass invalid input to save, should I throw an exception like this:

class AM_Products extends AM_Object 
{
    public function save( $new_data = array() ) 
    {
        // Validate input
        if ( ! validate( 'text', $new_data['name'] ) ) {
            throw new Exception( 'Invalid data entered' );
        }

        // Save input
    }
}

Or instead, should I add an extra function and leave it to the view/controller:

if ( $product->save( $data )->has_error() ) {
    $error = $product->get_error();
}

echo '<p>' . $error . '</p>';

Don't throw an exception. Exceptions are for exceptional situations - invalid data entered into a form should not trigger an exception.

Your model should have some sort of error state set, either on the model itself or on the individual fields. The post-back should "fall through" and display the same form that was originally shown, with error messages and/or highlighted fields indicating where the error is so the user can fix it.

Throwing exceptions for validation is going to lead to a very fragile and difficult to use system. What happens if you want to simply show the user that one of the fields they supplied is invalid and give them a chance to correct it? How are you going to catch an exception and know how to display the associated record/form?

Throw an exception. Otherwise you'll have to remember always to call has_error/get_error after any operation. And you'll have a lot of duplicated code. And what if the error should be handled not by the method a() that have called save(), but by the method b() that called the method a()? you'll have to return error from a(), and b() will have to check for the error as well.