## blPop, brPop ##### *Description* Is a blocking lPop(rPop) primitive. If at least one of the lists contains at least one element, the element will be popped from the head of the list and returned to the caller. Il all the list identified by the keys passed in arguments are empty, blPop will block during the specified timeout until an element is pushed to one of those lists. This element will be popped. lpop命令的block版本即阻塞版本。如果LIST容器中有VAULE，將會返回ARRAY（'listName''element'）。如果TIMEOUT參數為空，那么如果LIST為空，blPop或者brPop將或結束調用。如果設置了timeout參數，blPop或者brPop將被掛起暫停運行TIMEOUT參數的時間，在此期間如果LIST被PUSH了元素，將在TIMEOUT時間結束后，被POP出來。 ##### *Parameters* *ARRAY* Array containing the keys of the lists *INTEGER* Timeout Or *STRING* Key1 *STRING* Key2 *STRING* Key3 ... *STRING* Keyn*INTEGER* Timeout ##### *Return value* *ARRAY* array('listName', 'element') ##### *Example* ``` <pre class="calibre9">/* Non blocking feature */ $redis->lPush('key1', 'A'); $redis->delete('key2'); $redis->blPop('key1', 'key2', 10); /* array('key1', 'A') */ /* OR */ $redis->blPop(array('key1', 'key2'), 10); /* array('key1', 'A') */ $redis->brPop('key1', 'key2', 10); /* array('key1', 'A') */ /* OR */ $redis->brPop(array('key1', 'key2'), 10); /* array('key1', 'A') */ /* Blocking feature */ /* process 1 */ $redis->delete('key1'); $redis->blPop('key1', 10); /* blocking for 10 seconds */ /* process 2 */ $redis->lPush('key1', 'A'); /* process 1 */ /* array('key1', 'A') is returned*/ ```