What is the difference between public, private, and protected?

In PHP, public, private, and protected are access modifiers that control the visibility of class properties and methods.

  • public properties and methods can be accessed from anywhere, inside or outside the class.
  • private properties and methods can only be accessed from within the class.
  • protected properties and methods can be accessed from within the class or from a subclass (a class that extends the original class).

Here's an example:


class MyClass
    public $public_property = 'I am public';
    private $private_property = 'I am private';
    protected $protected_property = 'I am protected';

    public function publicMethod()
        // can access all properties and methods

    private function privateMethod()
        // can only access private properties and methods

    protected function protectedMethod()
        // can access protected properties and methods, as well as public properties and methods

$obj = new MyClass();

echo $obj->public_property; // outputs 'I am public'
echo $obj->private_property; // generates an error
echo $obj->protected_property; // generates an error

$obj->publicMethod(); // can be called
$obj->privateMethod(); // generates an error
$obj->protectedMethod(); // generates an error

Keep in mind that you cannot use private or protected access modifiers on properties or methods declared at the top level of a PHP script. They can only be used inside a class.