public function __construct(PDO $client, $table = 'cache')
{
$this->client = $client;
$this->table = $table;
// don't throw exceptions - it's ok to fail, as long as the return value
// reflects that!
$this->client->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_SILENT);
// make sure the database exists (or just "fail" silently)
$this->init();
// now's a great time to clean up all expired items
$this->clearExpired();
}