tester.php

<?php
class Tester
{
	private static $foo;

	public function __construct()
	{
		self::$foo = true;
	}

	public function bar()
	{
		if (self::$foo) {
			echo 'I can haz $foo';
		} else {
			echo 'No $foo';
		}
	}
}

$tester = new Tester;
$tester->bar();