Description:
------------
php > $memcache = new Memcached;
php > $memcache->addServer('localhost', 11211) or die ("Could not connect");
php > var_dump($memcache->set('key', 9223372036854775807));
bool(true)
php > var_dump($memcache->increment('key'));
int(-9223372036854775808)

The negative return value is a consequence of memcache->increment's use of atol to parse the results i.e.

  ...
  *number = (long) atol(mmc->inbuf);
  return 1;
}

memcache->increment should return the same thing as memcache->get for the key after increment.

Though I'm not sure if the clipping behavior of memcache->get is correct either:

php > var_dump($memcache->get('key'));
int(9223372036854775807)