PHP: One of ways to set/get a private/protected property. http://sandbox.onlinephpfunctions.com/code/d9caa381fe2a09473641e53b682194cd10b7096b

byClosure.php

<?php
class Item
{
    private $cost = 100;
    
    public function getTotal($discount = 7) {
       return $this->cost *(100+$discount)/100;
    }
}

class AccesserToPrivated
{
    public function getPrivate($obj, $attribute) {
        $getter = function() use ($attribute) {return $this->$attribute;};
        return \Closure::bind($getter, $obj, get_class($obj));
    }
    
    public function setPrivate($obj, $attribute) {
        $setter = function($value) use ($attribute) {$this->$attribute = $value;};
        return \Closure::bind($setter, $obj, get_class($obj));
    }
}

$obj = new Item();

$accesser = new AccesserToPrivated();
$getCost = $accesser->getPrivate($obj, 'cost');
$setCost = $accesser->setPrivate($obj, 'cost');

echo 'Cost ' . $getCost() . ', total ' . $obj->getTotal() . PHP_EOL;
$setCost(1); //set new cost
echo 'Cost ' . $getCost() . ', total ' . $obj->getTotal() . PHP_EOL;