title: Does PDO ever close persistent connections?
body: <p>I switched to using PDO persistent connections. I encountered situations where MySQL (correctly) closes a connection on its end (due to inactivity) and PDO doesn't pick up on it, keeps the connection available in its cache, and from that point on - any attempt to use this connection results in a failure.</p>
  
  <p>From what I've read this behavior is "by design" (to me it looks like PDO is going out of its way to not support persistent connections).</p>
  
  <p>Either way, I would like to know if PDO would <em>ever</em> close a connection in its pool. I get it that it doesn't check the connection's state, but is there any kind of timer or periodic cleanup, configurable or hard-coded?</p>