如何在Redis PHP中获得过期时间

Question

This is my source code in else part I can able to get the ttl value but if I again run the code I can't able to get the ttl value in initial stage.

$username = 'key';
$redis->set($username , 1);
$ttl = $redis->ttl( $username );

error_log("ttl =============> ".json_encode($ttl));

if($ttl>0){
    error_log("ttl =============> ".json_encode($ttl));
    $result= array("error"=>"user already blocked".$ttl);          
}else {
    $limit = 30;

    $redis->expire( $username , $limit);


$ttl = $redis->ttl( $username );
$result=array("error"=>"user blocked for one hour, time remaining is ".$ttl);