(PECL memcached >= 0.1.0)
Memcached::flush — Invalidate all items in the cache
$delay = 0
  ] )
   Memcached::flush() invalidates all existing cache items
   immediately (by default) or after the delay
   specified. After invalidation none of the items will be returned in
   response to a retrieval command (unless it's stored again under the same
   key after Memcached::flush() has invalidated the items).
   The flush does not actually free all the memory taken up by the existing
   items; that will happen gradually as new items are stored.
  
delayNumber of seconds to wait before invalidating the items.
   Returns TRUE on success or FALSE on failure.
   Use Memcached::getResultCode() if necessary.
  
Example #1 Memcached::flush() example
<?php
$m = new Memcached();
$m->addServer('localhost', 11211);
/* flush all items in 10 seconds */
$m->flush(10);
?>