如何从redis到php变量获取值？

Question

this is my source code . I want to get the values of username from redis to the $check variable ? and iam beginner to the php & redis .

$username = $_POST['username'];
$redis = new Redis(); 
$redis->connect('127.0.0.1', 6379);
$redis->set( $username , 1);
$redis->exists( $username ); 
$check = $redis->get( $username );