描述正在尝试安装laelaps/symfony-gearman-bundle通过composerrequirelaelaps/symfony-gearman-bundle有一些错误，我很难理解它们的意思。错误Problem1-laelaps/symfony-gearman-bundle1.1.x-devrequiresext-gearman*->therequestedPHPextensiongearmanismissingfromyoursystem.-laelaps/symfony-gearman-bundle1.x-devrequiresext-gearman*->therequ