有没有适用于PHP的完整功能作业调度软件包？我正在寻找PHP版本的Java的Quartz。我可以让事情从cron外部触发来驱动系统。我需要的功能是：

• Ability to register task (class/method) to be called at given intervals.
• Ability to specify whether a given task can be run multiple times (potentially long running methods should not be run multiple times in certain cases).
• All registered entries/methods could be run in parallel (jobs are backgrounded so that they do not block other timed tasks).
• Ability to set a timeout for a given task.
• Ability to update job control dynamically, so for instance you could disable some tasks or change their frequency without code changes.

我知道这很难要求，但这似乎是一个有用的功能批次，我想有人可能已经把它们的一部分组合在一起了。

如果这个或其中某个部分还不存在，是否能提供一些指导来组装它，或者提供一个已经拥有某些功能实现具有合理性的开源项目？