<?php

class Test {
	protected $var = 5;
	public function getVar() {
		echo $this->var, PHP_EOL;
	}
}

$obj = new Test;
$obj->getVar();

$refObj = new ReflectionObject( $obj );
$refProp = $refObj->getProperty( 'var' );
$refProp->setAccessible( true );
$refProp->setValue( $obj, 555 );

$obj->getVar();