derick@kossu:/tmp$ cat test.php
<?php
class foo {
	private $bar = 42;
}

$obj = new foo;

$f = new ReflectionObject( $obj );
$p = $f->getProperty( 'bar' );
$p->setAccesible( true );
echo $p->getValue( $obj ), "\n";
?>
derick@kossu:/tmp$ ~/dev/php/php-5.3dev/sapi/cli/php test.php 
42