system/Cache/Handlers/FileHandler.php
protected function getItem(string $key)
	{
		if (! is_file($this->path . $key))
		{
			return false;
		}

		$data = unserialize(file_get_contents($this->path . $key));

		if ($data['ttl'] > 0 && time() > $data['time'] + $data['ttl'])
		{
			unlink($this->path . $key);

			return false;
		}

		return $data;
	}
protected function getItem(string $key)
	{
		if (! is_file($this->path . $key))
		{
			return false;
		}

		$data = unserialize(file_get_contents($this->path . $key));

		if ($data['ttl'] > 0 && time() > $data['time'] + $data['ttl'])
		{
			unlink($this->path . $key);

			return false;
		}

		return $data;
	}
Does the heavy lifting of actually retrieving the file and
verifying it's age.

@param string $key

@return boolean|mixed