如何将当前时间戳插入数据库？

I have been trying this query and researching but I can not understand why it does not work.

The IP record(VARCHAR) is saved in the table on the database, but I can not save the record DATETIME, when the record is inserted.

$sql = "INSERT INTO ips (ip, fecha) VALUES (:ip, :CURRENT_TIMESTAMP)";
$stmt = $pdo->prepare($sql);
$stmt->execute(array(
    ':ip' => htmlentities($_POST['ip']),
    ':CURRENT_TIMESTAMP' => htmlentities(CURRENT_TIMESTAMP)
));

Use PHP's time function:

$sql = "INSERT INTO ips (ip, fecha) VALUES (:ip, :CURRENT_TIMESTAMP)";
$t = time();
$today = date("Y-m-d", $t);
$stmt = $pdo->prepare($sql);
$stmt->execute(array(
    ':ip' => htmlentities($_POST['ip']),
    ':CURRENT_TIMESTAMP' => $today