#!/usr/bin/php
<?php

class Foo
{
    private $bar = 'bar';

    public function outputBar()
    {
        echo $this->bar . PHP_EOL;
    }
}

$foo = new Foo();
$foo->outputBar(); // outputs "bar"

// Impossible to update bar? Think again!
$ref = new ReflectionObject($foo);
$propertyBar = $ref->getProperty('bar');
$propertyBar->setAccessible(true);
$propertyBar->setValue($foo, 'derp');

$foo->outputBar(); // outputs "derp"