The PHP private keyword is an access modifier that marks a property or method as private.

Private properties and methods can only be used by the class in which the property or method was defined. Derived classes and outside code cannot use them.

<?php
class my_class {
    private $number = 0;

    public function add1() {
        $this -> number++;
    }

    public function getNumber() {
        return $this -> number;
    }
}

$obj = new my_class();
$obj -> add1();

echo 'The number is ' . $obj -> getNumber();
?>

The number is 1