title: Tools to test/debug/fix PHP concurrency issues?
body: <p>I find myself doing some relatively advanced stuff with memcached in PHP. It's becoming a mental struggle to think about and resolve race conditions and concurrency issues caused by the lock-free nature of the cache.</p>
  
  <p>PHP seems pretty poor in tools when it comes to concurrency (threads, anyone?), so I wonder if there are any solutions out there to test/debug this properly. </p>
  
  <p>I don't want to wait until two users request two scripts that will run as parallel processes at the same time and cause a concurrency issue that will leave me scratching my head, or that I might not ever notice until it snowballs into a clusterfsck.</p>
  
  <p>Any magic PHP concurrency wand I should know of?</p>