Calling the variable property directly vs getter/setters - OOP Design

Question

I know this is probably subjective but I read this optimization page from Google for PHP and they suggest use the variable property directly without the need of getters and

Answer 1

You could also use the __get and __set magic methods:

class Example
{
    private $allowedProps = array('prop1', 'prop2', 'prop3');
    private $data = array();

    public function __set($propName, $propValue)
    {
        if (in_array($propName, $this->allowedProps))
        {
            $this->data[$propName] = $propValue;
        }
        else
        {
            // error
        }
    }

    public function __get($propName)
    {
        if (array_key_exists($propName, $this->data))
        {
            return $this->data[$propName];
        }
        else
        {
            // error
        }
    }
}