PHP OOP -> protected method can only be called in child class only, not an instance of child

 <?php

// The following will result error, as protected method parentTesterFunction () is called on instance of child.

class ParentTester {

    

    protected function parentTesterFunction () {

        echo "parent function";

    }

    

}

class ChildTester extends ParentTester {

   

}

$childTester = new ChildTester();

$childTester->parentTesterFunction();

--------------Result --------

<br />

<b>Fatal error</b>:  Uncaught Error: Call to protected method ParentTester::parentTesterFunction() from context '' in [...][...]:19

Stack trace:

#0 {main}

  thrown in <b>[...][...]</b> on line <b>19</b><br />

--------------------------------------------------------------------------------------------------

Following will work 

<?php

class ParentTester {

    

    protected function parentTesterFunction () {

        echo "parent function";

    }

    

}

class ChildTester extends ParentTester {

    

    public function parentTesterFunction() {

        return parent::parentTesterFunction();

    }

    

}

$childTester = new ChildTester();

$childTester->parentTesterFunction();

--------------Result --------

parent function