php without __get function, you can't get a value from certain instances?

Since my tech book told me so, I'm wondering if that's true, for example:

class A {
    public $attr = "hmm";
}

$a = new A();
echo $a->attr; // outputs hmm

well that works for me, the book says not in order to use it outside class it's not making a __get function. i'm confused a bit.

Both public variables and magical __get() methods are considered to be a bad practice. First ones cause objects to loose the data encapsulations, while magic getters/setters attract complexity.

It is common to performs some operations on the data in the setter, before it is assigned to a parameter. For example, you would validate email address. Or format of phone number. When instead you use magical __get and __set methods, you will have to do all of this in a single method.

Essentially, your magical setter turns in a huge cluster*uck of if .. else statements of various depth.

Instead you should make a custom getter for instance's parameter that you want to manipulate:

class Book
{
    private $title;
    private $author;

    public function __construct( $author = null, $author = null )
    {
        $this->title = $title;
        $this->author = $author;
    }

    public function setTitle( $title)
    {
        $this->title = $title;
    }

    public function setAuthor( $author)
    {
        $this->author = $author;
    }

}

Which is used as:

$instance = new Book('Jim Butcher');
$isntance->setTitle('Fool Moon');