致命错误：在非对象中调用成员函数close（）

Question

首先，请记住，我已经尝试解决这个问题了一个小时，所以请不要“判断”我要发布的问题已经被回答了……我在这里访问了这些帖子：

致命错误：在非对象上调用成员函数close（）。 MySQLi问题和http://w3guy.com/fatal-error-call-member-function-fetch_object-non-object/

但是这些有点对我不起作用，我也不知道为什么...

我的密码：

<?php
include_once 'db_connect.php';
include_once 'psl-config.php';

$error_msg = "";

if (isset($_POST['username'], $_POST['email'], $_POST['p'])) {
    // Sanitize and validate the data passed in
    $username = filter_input(INPUT_POST, 'username', FILTER_SANITIZE_STRING);
    $email = filter_input(INPUT_POST, 'email', FILTER_SANITIZE_EMAIL);
    $email = filter_var($email, FILTER_VALIDATE_EMAIL);
    if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        // Not a valid email
        $error_msg .= '<p class="error">The email address you entered is not valid</p>';
    }

    $password = filter_input(INPUT_POST, 'p', FILTER_SANITIZE_STRING);

    // Username validity and password validity have been checked client side.
    // This should should be adequate as nobody gains any advantage from
    // breaking these rules.
    //

    $prep_stmt = "SELECT id FROM members WHERE email = ? LIMIT 1";
    $stmt = $mysqli->prepare($prep_stmt);

   // check existing email  
    if ($stmt) {
        $stmt->bind_param('s', $email);
        $stmt->execute();
        $stmt->store_result();

        if ($stmt->num_rows == 1) {
            // A user with this email address already exists
            $error_msg .= '<p class="error">A user with this email address already exists.</p>';
                        $stmt->close();
        }
                $stmt->close();
    } else {
        $error_msg .= '<p class="error">Database error Line 39</p>';
                $stmt->close();
    }

    // check existing username
    $prep_stmt = "SELECT id FROM members WHERE username = ? LIMIT 1";
    $stmt = $mysqli->prepare($prep_stmt);

    if ($stmt) {
        $stmt->bind_param('s', $username);
        $stmt->execute();
        $stmt->store_result();

                if ($stmt->num_rows == 1) {
                        // A user with this username already exists
                        $error_msg .= '<p class="error">A user with this username already exists</p>';
                        $stmt->close();
                }
                $stmt->close();
        } else {
                $error_msg .= '<p class="error">Database error line 55</p>';
                $stmt->close();
        }

    // TODO: 
    // We'll also have to account for the situation where the user doesn't have
    // rights to do registration, by checking what type of user is attempting to
    // perform the operation.

    if (empty($error_msg)) {

        // Create salted password 
        $passwordHash = password_hash($password, PASSWORD_BCRYPT);

        // Insert the new user into the database 
        if ($insert_stmt = $mysqli->prepare("INSERT INTO members (username, email, password) VALUES (?, ?, ?)")) {
  $insert_stmt->bind_param('sss', $username, $email, $passwordHash);
            // Execute the prepared query.
            if (! $insert_stmt->execute()) {
                header('Location: ../error.php?err=Registration failure: INSERT');
            }
        }
        header('Location: ./continue.php');
    }
}

Answer 1

if ($stmt->num_rows == 1) {
     $error_msg .= '<p class="error">A user with this email address already exists.</p>';
     $stmt->close();
}
$stmt->close();

应该

if ($stmt->num_rows == 1) {
    $error_msg .= '<p class="error">A user with this email address already exists.</p>';
    $stmt->close();
} else {
    $stmt->close();
}

否则，如果num_rows == 1，则将其关闭两次。

或更好：

if ($stmt->num_rows == 1) {
    $error_msg .= '<p class="error">A user with this email address already exists.</p>';
}
$stmt->close();

另一个事实是：在IF($stmt)的ELSE ，您不能执行$stmt->close(); 因为$stmt不存在。