PHP. Руководство по PHP. 2005
Memcache::increment
Memcache::increment
Description
int Memcache::increment (string key [, int value])Memcache::increment() increments value of the item on the specified value. If item with key key was not numeric and cannot be converted to number, it will change it's value to value.
Parameter value is optional. It's default value is 1.
Замечание: Do not use Memcache::increment() with item, which was stored compressed, because consequent call to Memcache::get() will fail.