Returns the keys in a hash, as an array of strings.
取得HASH表中的KEYS，以数组形式返回。
Parameters
Key: key
Return value
An array of elements, the keys of the hash. This works like PHP's array_keys().
Example
$redis->delete('h');
$redis->hSet('h', 'a', 'x');
$redis->hSet('h', 'b', 'y');
$redis->hSet('h', 'c', 'z');
$redis->hSet('h', 'd', 't');
var_dump($redis->hKeys('h'));
Output:
array(4) {
[0]=>
string(1) "a"
[1]=>
string(1) "b"
[2]=>
string(1) "c"
[3]=>
string(1) "d"
}
The order is random and corresponds to redis' own internal representation of the set structure.
