Description
Remove specified keys.
移除已经存在KEYS
Parameters
An array of keys, or an undefined number of parameters, each a key: key1 key2 key3 ... keyN
可以是一个KEYS的数组，或者一个未定义的数字参数，或者一个一个的写KEY
Return value
Long Number of keys deleted.
返回删除KEY-VALUE的数量
Examples
$redis->set('key1', 'val1');
$redis->set('key2', 'val2');
$redis->set('key3', 'val3');
$redis->set('key4', 'val4');
$redis->delete('key1', 'key2'); /* return 2 */
$redis->delete(array('key3', 'key4')); /* return 2 */
