access modifiers

Let's test the access modifiers we learned earlier.

protected test

protected can also be used in declared classes, and can also be used in inherited child classes.

<?php
    class parents
    {
        protected $parents = "Parental car";
    }

    class child extends parents
    {
        public function rentCar()
        {
            return "Borrow a {$this->parents}";
        }
    }

    $test = new child;
    echo $test->rentCar();
?>

Result of the code above

The above code declared a property as protected in the parent class. So you could use that property in a child class.
This time, I'll change protected to private in the same code.
Then, of course, it is a property that can only be used in a parent class, so it cannot be used in a child class.

<?php
    class parents
    {
        private $parents = "Parental car";
    }

    class child extends parents
    {
        public function rentCar()
        {
            if(isset($this->parents)){
                return "Borrow a {$this->parents}";
            } else {
                return "I can't rent a car.";
            }
        }
    }

    $test = new child;
    echo $test->rentCar();
?>

Result of the code above

The isset function determines whether the variable is present and returns true if it exists and false if it does not exist.