title: PHP Garbage Collection clarification
body: <p>From the PHP manual, session.gc_probability and session.gc_divisor state that gc will occur based on this probability. I get that.</p>
  
  <p>What I'm not clear on is whether this probability is on a session by session basis or overall.</p>
  
  <p>So if my probability is 1% (1/100) that GC will occur, does that mean that if one session keeps getting extended, each time there is a 1% change that specific session will be cleaned up? Or does this mean that 1% of all existing sessions (as well as new ones) will trigger GC for all other existing sessions?</p>
  
  <p>I'm pretty sure it's the latter, I just want to make sure. </p>
  
  <p>The purpose of this question is that on our site, I want users to have long-term sessions (6 months). If 1% of all sessions trigger GC, then that effectively removes the purpose of having that long-term session, as GC will end up occurring every hour or two.</p>