MySQL - 更新数据库中的登录时间

Question

I am currently working on a project where I need to store information in a database for member login page. Currently, I am working on storing the time the user enters their credentials. It keeps popping up with "Duplicate entry '0000-00-00 00:00:00' for key 'PRIMARY'", which I understand everything except for why my time will not process as an actual time... Below the section of my code that I am working with... maybe something is wrong? Or is there a better way to call the current timestamp than what I am doing.

    $mysqli = new mysqli(HOST, USER, PASSWORD, DATABASE)
or die("Failed to connect");
if(isset($_POST['submit'])) {
    date_default_timezone_set('America/Phoenix');
    $username = mysql_real_escape_string($_POST['userlogin']); 
    $password = mysql_real_escape_string($_POST['userpassword']);
    $today = date("F j, Y, h:i:s A"); 
    $sql = "SELECT * FROM Member WHERE loginName = '".$username."' AND password = '".$password."'"; //checks for user in database
    //--password = SHA2(CONCAT('bar','paz'),512)";
    $result = $mysqli->query($sql) or die($mysqli->error); //shoots an error if something is wrong
    if($result->num_rows < 1) // if the username/password is incorrect then an error message appears
       {
        echo "Invalid username/password combination. Please try again.";
       }
    else
       {
        echo "Welcome."; //Successful
        $today = date("F j, Y, h:i:s A"); 
        header('Location: thankspage.html');
     $sql = " INSERT INTO Login (loginName,loginTime) 
       VALUES ('$username', '$today' ) "; // creates the login time.
    $result = $mysqli->query($sql) or die ($mysqli->error); // shoots an error if i did something wrong.
   }
}   

Answer 1

Either change the datetime format

$today = date("F j, Y, h:i:s A");

to a proper one

$today = date("Y-m-d H:i:s");

Here is Codepad demo

or ditch $today altogether and use NOW() on MySQL side (if the timezone setting is the same as on the web server)

INSERT INTO Login (loginName, loginTime) VALUES ('$username', NOW())
                                                              ^^^^^

On a side note: since you already using mysqli consider to learn and use prepared statements instead of interpolating query strings, which leaves you wide open to sql injections.