PHP登录脚本问题

Question

i was wondering if anyone could help as i am trying to adapt a PHP login script to accept only the password without the need for the username and I don't know what i am doing wrong.

I am a complete novice i am afraid.

What i want the end result to be is for any user to type in one password, the script then checks the password is correct from my data base and then logs them in.

//First we start a session
session_start();

//We then check if the user has clicked the login button
if (isset($_POST['submit'])) {

    //Then we include the database connection
    include_once 'dbh.inc.php';
    //And we get the data from the login form
    $pwd = $_POST['pwd'];

    //Error handlers
    //Error handlers are important to avoid any mistakes the user might have made when filling out the form!
    //Check if inputs are empty
    if (empty($pwd)) {
        header("Location: ../index.php?login=empty");
        exit();
    }
    else {
        //Check if username exists in the database USING PREPARED STATEMENTS
        $sql = "SELECT * FROM users WHERE user_uid=?";
        //Create a prepared statement
        $stmt = mysqli_stmt_init($conn);
        //Check if prepared statement fails
        if(!mysqli_stmt_prepare($stmt, $sql)) {
            header("Location: ../index.php?login=error");
            exit();
        }
        //If the prepared statement didn't fail, then continue
        else {
            //Bind parameters/data to the placeholder (?) in our $sql
            mysqli_stmt_bind_param($stmt, "s", $uid);

            //Run query in database
            mysqli_stmt_execute($stmt);

            //Get results from query
      $result = mysqli_stmt_get_result($stmt);

            //If we had a result, which means the username does exist, then assign the database row data to $row.
            if ($row = mysqli_fetch_assoc($result)) {
                //De-hashing the password using the password provided by the user, and the password from the database, to see if they match.
                $hashedPwdCheck = password_verify($pwd, $row['user_pwd']);
                //If they didn't match!
                if ($hashedPwdCheck == false) {
                    header("Location: ../index.php?login=error");
                    exit();
                }
                //If they did match!
                elseif ($hashedPwdCheck == true) {
                    //Set SESSION variables and log user in
                    $_SESSION['u_id'] = $row['user_id'];
                    $_SESSION['u_first'] = $row['user_first'];
                    $_SESSION['u_last'] = $row['user_last'];
                    $_SESSION['u_email'] = $row['user_email'];
                    $_SESSION['u_uid'] = $row['user_uid'];
                    header("Location: ../index.php?login=success");
                    exit();
                }
      } else {
        header("Location: ../index.php?login=error");
            exit();
      }
        }
    }

    //Close the prepared statement
    mysqli_stmt_close($stmt);

} else {
    header("Location: ../index.php?login=error");
    exit();
}

Answer 1

You are binding $uid which is undefined:

   //Bind parameters/data to the placeholder (?) in our $sql
    mysqli_stmt_bind_param($stmt, "s", $uid);