Description
Return and remove the first element of the list.
返回LIST顶部（左侧）的VALUE，并且从LIST中把该VALUE弹出。
Parameters
key
Return value
STRING if command executed successfully BOOL FALSE in case of failure (empty list)
取得VALUE成功，返回TURE。如果是一个空LIST则返回FLASE。
Example
$redis->rPush('key1', 'A');
$redis->rPush('key1', 'B');
$redis->rPush('key1', 'C'); /* key1 => [ 'A', 'B', 'C' ] */
$redis->lPop('key1'); /* key1 => [ 'B', 'C' ] */
