(PECL memcached >= 2.0.0)
Memcached::incrementByKey — Increment numeric item's value, stored on a specific server
$server_key,$key,$offset = 1,$initial_value = 0,$expiry = 0
Memcached::incrementByKey() increments a numeric item's value
by the specified offset. If the item's value is not
numeric, an error will result.
Memcached::incrementByKey() will set the item to the
initial_value parameter if the key doesn't exist.
server_key本鍵名用于識別儲存和讀取值的服務(wù)器。沒(méi)有將實(shí)際的鍵名散列到具體的項目，而是在決定與哪一個(gè) memcached 服務(wù)器通信時(shí)將其散列為服務(wù)器鍵名。這使得關(guān)聯(lián)的項目在單一的服務(wù)上被組合起來(lái)以提高多重操作的效率。
keyThe key of the item to increment.
offsetThe amount by which to increment the item's value.
initial_valueThe value to set the item to if it doesn't currently exist.
expiryThe expiry time to set on the item.
Returns new item's value on success 或者在失敗時(shí)返回 false.