<?php
class Foo {
	public $first;
	public $second;
	
	public static $array = array();
	
	public function __construct($first, $second) {
		$this->first = $first;
		$this->second = $second;
		
		self::$array[] = $this;
	}
}

$first = new Foo('first', 'first');
$second = new Foo('second', 'second');

print_r(Foo::$array);