dump
Description
Dump a key out of a redis database, the value of which can later be passed into redis using the RESTORE command. The data that comes out of DUMP is a binary representation of the key as Redis stores it.
把一个KEY从REIDS中销毁(但是这个销毁不是物理意义上销毁),这个被销毁的VALUE，可以使用RESTORE函数恢复出来。使用DUMP销毁的VALUE，函数将返回这个数据在REIDS中的二进制内存地址。
Parameters
key string
Return value
The Redis encoded value of the key, or FALSE if the key doesn't exist
Examples
$redis->set('foo', 'bar');
$val = $redis->dump('foo'); // $val will be the Redis encoded key value