Describes the object pointed to by a key.
声明一个对象，并指向KEY。
Parameters
The information to retrieve (string) and the key (string). Info can be one of the following:
"encoding"
"refcount"
"idletime"
Return value
STRING for "encoding", LONG for "refcount" and "idletime", FALSE if the key doesn't exist.
Example
$redis->object("encoding", "l"); // → ziplist
$redis->object("refcount", "l"); // → 1
$redis->object("idletime", "l"); // → 400 (in seconds, with a precision of 10 seconds).