key = $key; } /** @var int|string */ protected $key; function exists($src): bool { return $this->key !== null && cl::has($src, $this->key); } function get($src, $default=null) { if ($this->key === null) return $default; return cl::get($src, $this->key, $default); } function set($value, &$dest): void { if ($this->key === null) return; cl::set($dest, $this->key, $value); } function del(&$dest): void { if ($this->key === null) return; cl::del($dest, $this->key); } }