Javascript window.location.href and window.alert

Question

How can Javascript window.location.href and window.alert can work together inside if else cycle?

I have the following code to insert data inside an SQL table. If something wrong, a notice message appear (Notice: Undefined variable: code1 in......) for just a second because of window.location.href redirection and the alert (messagebox) don't appear.

if(isset($_POST['add_item'])){
    $edit_id = $_POST['edit_id'];
    $code = $_POST['code'];
    $sql = "INSERT INTO table (code) 
                       VALUES ('$code1')";
    if ($conn->query($sql) === TRUE) {
        echo '<script type="text/javascript">window.location.href="page.php"</script>';
    } else {
        //echo "Error: " . $sql . "<br>" . $conn->error;
        echo '<script type="text/javascript">alert("Error: ' . $sql . "<br>" . $conn->error .'")</script>';
        }   
}

$code1 inside VALUES into $SQL was deliberately placed to generate the error. Is there a way to redirect if all is OK and open the messagebox if an error appear

Answer 1

You could simply use header() on server side if you want to forward:

    if ($conn->query($sql) === TRUE) {
        header("Location: page.php");
    } else {
        echo '<script type="text/javascript">
alert("Error: ' . $sql . "\n" . $conn->error .'")</script>';
//use backslash for break in alert…
        } 

BTW: don't forget semicolon terminating each line…

AND USE PREPARED STATEMENTS!