gistfile1.php

<?php

$cache = array();

$insert = function(stdClass $stat) use(&$cache) {
  echo 'insert '; var_dump($stat->i);
	$cache[spl_object_hash($stat)] = $stat;
};

$delete = function(stdClass $stat) use(&$cache) {
	echo 'delete '; var_dump($stat->i);
	unset($cache[spl_object_hash($stat)]);
};

class Test {
	private static $n = 0;
	private $stat;
	private $delete;
	public function __construct($insert, $delete) {
		$this->delete = $delete;
		$this->stat = new stdClass();
		$this->stat->i = self::$n++;
		echo 'construct '; $this->stat();
		$insert($this->stat);
	}
	public function __destruct() {
		echo 'destruct '; $this->stat();
		$delete = $this->delete;
		$delete($this->stat);
	}
	public function stat() {
		var_dump($this->stat->i);
	}
}

echo '<pre>';

$a = new Test($insert, $delete);
$b = new Test($insert, $delete);

unset($a);

echo 'script end' . PHP_EOL;