Lithium Docs

						public function testKeyWithClosure() {
		$value = 5;

		$key = function() use ($value) {
			return "closure key {$value}";
		};

		$result = Cache::key($key);
		$expected = 'closure key 5';
		$this->assertIdentical($expected, $result);

		$reference = 'mutable';

		$key = function () use (&$reference) {
			$reference .= ' key';
			return $reference;
		};

		$result = Cache::key($key);
		$expected = 'mutable key';
		$this->assertIdentical($expected, $result);
		$this->assertIdentical('mutable key', $reference);
	}