## watch, unwatch ##### Description Watches a key for modifications by another client. If the key is modified between `<span class="calibre12">WATCH</span>` and `<span class="calibre12">EXEC</span>`, the MULTI/EXEC transaction will fail (return `<span class="calibre12">FALSE</span>`). `<span class="calibre12">unwatch</span>` cancels all the watching of all keys by this client. 監控一個KEY是否被其他的客戶端修改。如果KEY在調用watch()和exec()之間被修改，那么批量處理最終的exec()執行將失敗。unwatch()取消對于所有KEY值的監控操作針對于這個Redis實例。通過一些實驗，這個函數的效果其實并沒有那么好，或者說不能夠準確的去監控。 ##### Parameters *keys*: a list of keys ##### Example ``` <pre class="calibre9">$redis->watch('x'); /* long code here during the execution of which other clients could well modify `x` */ $ret = $redis->multi() ->incr('x') ->exec(); /* $ret = FALSE if x has been modified between the call to WATCH and the call to EXEC. */ ```