<?php

class Foo {
	public function returnToTheBar(Bar $bar) {
		$bar->getFoo($this);
	}
}

class Bar {
	public $foo;
	
	public function getFoo($foo) {
		$this->foo = $foo;
	} 
}


$Foo = new Foo();
$Bar = new Bar();

$Foo->returnToTheBar($Bar);

var_dump($Foo);

var_dump($Bar->foo);