Question

Here is my php class:

class Category {
    private $cat_id;
    private $cat_name;
    private $cat_is_main;
    private $cat_parent;

    function __get($key) {
        switch ($key) {
            case 'cat_id':
                return $this->cat_id;
            case 'cat_name':
                return $this->cat_name;
            case 'cat_is_main':
                return $this->cat_is_main;
            case 'cat_parent':
                return $this->cat_parent;
        }
    }

    function __set($key, $value) {
        switch ($key) {
            case 'cat_id':
                $this->cat_id = (int) $value;
                break;
            case 'cat_name':
                $this->cat_name = (string) $value;
                break;
            case 'cat_is_main':
                $this->cat_is_main = (bool) $value;
                break;
            case 'cat_parent':
                $this->cat_parent = (int) $value;
                break;
        }
    }
}
$conn = new mysqli($server, $username, $password, $dbname);
if ($result = $conn->query('SELECT cat_id, cat_name FROM categories WHERE cat_id = 1;')) {
    var_dump($result->fetch_object('Category'));
}

And I got:

object(Category)#5 (4) {
    ["cat_id":"Category":private]=> string(1) "1"
    ["cat_name":"Category":private]=> string(9) "test data"
    ["cat_is_main":"Category":private]=> string(1) "1"
    ["cat_parent":"Category":private]=> string(1) "0"
}

What I’m expecting is something like:

object(Category)#1 (4) {
    ["cat_id":"Category":private]=> int(1)
    ["cat_name":"Category":private]=> string(9) "test data"
    ["cat_is_main":"Category":private]=> bool(true)
    ["cat_parent":"Category":private]=> int(0)
}

It seem the mysqli_fetch_object() does not use my __set() method when create new object. It just some how set value for my private properties directly.
Is this normal in PHP? Is there anything else I can do to get what I want?
Thanks!

Answer 1

When mysqli_fetch_object() creates an object, it basically creates a stdClass first with all of the attributes set and then switches the object’s class to the one you supplied and then runs the constructor. As you noticed, the __set() method doesn’t get called, but that is normal and just how the function works.