Question

出于某种原因，当我在表单中输入现有的用户名和密码时，输出总是'用户不存在'，我怎么能改变它以便如果用户存在则将用户带到welcome.php页面如果用户没有，则“用户不存在”。该数据库名为TEST，该表名为USERS。

<?php 
    $servername = "localhost";
    $username = "root";
    $password = "";
    $dbname = "test";

// Create connection
    $conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
    if ($conn->connect_error) {
        die("Connection failed: " . $conn->connect_error);
    }

    $user = $conn->real_escape_string($_POST['username']);
    $pass = $conn->real_escape_string($_POST['password']);

    $query = "SELECT `username` AND `password` FROM `users` WHERE `username` = '$user' AND `password` = '$pass'";

    $result = $conn->query($query);
    if($result->num_rows < 0) {

       header('Location:welcome.php');
       die();
    }
    else $message = 'User does not exist';
?>

    <!DOCTYPE html>
    <html>
        <head>
            <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
            <title>Test</title>
        </head>

        <body>
            <form method="post" action="testing.php" enctype="multipart/form-data">
                <?php if(isset($message)) : ?>
                    <div class="error"><?php echo $message; ?></div>
                <?php endif; ?>

                Username: <input type="text" value="" name="username" /><br /><br />
                Password: <input type="text" value="" name="password" /><br /><br />
                <input type="submit" name="submit" value="Log In"/><br /><br />
                <a href="register.php">Register</a>
            </form>
        </body>
    </html>

Answer 1

num_rows()永远不会返回小于零。它会在失败时返回布尔值false，或0或正整数。如果用户不存在或提供了错误的密码，则将返回零行：

if ($result->num_rows == 0) {
     die("Wrong user/pass");
} else if ($result->num_rows > 1) {
     die("Duplicate user accounts!");
} else {
     die("Welcome");
}

如何检查数据库php中是否存在用户

1 个答案: