“if”陈述中的三个“elses”

Is it possible to have an if statement with three else parts?

My login script checks the username, password and captcha. If the user/pass or captcha is wrong, the site return with an error saying "username or password incorrect". But I also want it to give an error when there are blank fields (just one is sufficient to give the error). I thought I could just add a third else{ but Dreamweaver gives an error.

How can I achieve this?

<?php
$username=$_POST["username"];
$password=$_POST["password"];

$username = stripslashes($username);
$password = stripslashes($password);
$username = mysqli_real_escape_string($con, $username);
$password = mysqli_real_escape_string($con, $password);
$query = mysqli_query($con, "SELECT * FROM $tbl_name WHERE username='$username' and password='$password'");
$result = mysqli_num_rows($query);

if($result===1){
    session_start();
    $_SESSION["username"] = $username;
    if(isset($_POST["captcha"])&&$_POST["captcha"]!=""&&$_SESSION["code"]==$_POST["captcha"])
    {
        header('location:admin.php');
        exit();
    }
    else{
        session_destroy();
        die(header("location:lgin.php?codeFailed=true&reason=code&user=$username"));
        exit();
    }
}
else{
    session_destroy();
    die(header("location:lgin.php?loginFailed=true&reason=login"));
    exit();
}
else{ //dreamweaver gives an error here
    session_destroy();
    die(header("location:lgin.php?blank=true&reason=blank"));
    exit();
}
?>

There can be only one else per if statement. If you are nesting if statement .. you can have more else .. but still one else block per if statement. As I see it , you have two if conditions and three else blocks. That will not work .. you will need to remove one last dangling else.

Also it will improve your code readability if you indent it properly.

    if ($result === 1) {
        session_start();
        $_SESSION["username"] = $username;
        if (isset($_POST["captcha"]) && $_POST["captcha"] != "" && $_SESSION["code"] == $_POST["captcha"]) {
            header('location:admin.php');
            exit();
        } else {
            session_destroy();
            header("location:lgin.php?codeFailed=true&reason=code&user=$username")
            exit();
        }
    } else {
        session_destroy();
        header("location:lgin.php?loginFailed=true&reason=login")
        exit();
    }

You may want to use else if ... just in case you have more conditions to check. It will help if you visually draw a flowchart to see what you really want to achieve and then code it.

The code can be improved a lot .. but I guess that's not your primary concern here so I am leaving that .