Description
Sets a value and returns the previous entry at that key.
设置一个VALUE 并且返回该KEY当前的VALUE。
Parameters
Key: key
STRING: value
Return value
A string, the previous value located at this key.
Example
$redis->set('x', '42');
$exValue = $redis->getSet('x', 'lol'); // return '42', replaces x by 'lol'
$newValue = $redis->get('x')' // return 'lol'
