不删除私钥

Question

I want to set an expiration time for the private key that a user has.

I use PHP version 7.3.4.

<?php
error_reporting(E_ALL);
ini_set('display_errors', 1);
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
require ('config.php');
$expiration = time() + 60;
$sql = 'DELETE * FROM private_keys WHERE created < "'.$expiration.'"';
$result = $conn->query($sql) or die($conn->error);
?>

Expected the query to be executed, to delete all the expired private keys.