Question

如果有人能证实，我很乐意欣赏它。这可能是一个副本，我不知道。我查找了很多方法来检查数据库中的相同用户名，这是我的结果。我也会接受改进。

$con = mysqli_connect("localhost", "root", "", "testdb") or die("Error " . mysqli_error($con));
$result = mysqli_query($con, "SELECT * FROM users WHERE username = '".$username."'");
if ($row = mysqli_fetch_array($result) > 0) {
     if ($_POST['username'] == $row['username']){
    $error = true;
    $username_error = "Username is already in use.";
     }
}

编辑：完整代码：

    <?php
session_start();

if(isset($_SESSION['user_id'])) {
    header("Location: index.php");
}

include_once 'dbconnect.php';

//set validation error flag as false
$error = false;

//check if form is submitted
if (isset($_POST['signup'])) {
    $first_name = mysqli_real_escape_string($con, $_POST['first_name']);
    $last_name = mysqli_real_escape_string($con, $_POST['last_name']);
    $username = mysqli_real_escape_string($con, $_POST['username']);
    $email = mysqli_real_escape_string($con, $_POST['email']);
    $password = mysqli_real_escape_string($con, $_POST['password']);
    $cpassword = mysqli_real_escape_string($con, $_POST['cpassword']);
    $quote = mysqli_real_escape_string($con, $_POST['quote']);
    $who = mysqli_real_escape_string($con, $_POST['who']);

    //name can contain only alpha characters and space
        $db = new PDO("mysql:host=localhost;dbname=testdb;charset=utf8", "root", "awesome1426!$@^");
        $query = $db->prepare("SELECT * FROM users WHERE username=?");
        $query->bindParam(1, $username, PDO::PARAM_STR);
        if ($query->fetch()) {
            // Username is duplicate
            $error = true;
            $username_error = "no";
        } else {

        }

    if (!preg_match("/^[a-zA-Z ]+$/",$first_name)) {
        $error = true;
        $firstname_error = '<div class="error-notice">
                            <div class="oaerror danger">
                            <strong>Uh oh!</strong> - First Name must contain only alphabets and space.
                            </div>';

    }

    if (!preg_match("/^[a-zA-Z ]+$/",$last_name)) {
        $error = true;
        $lastname_error = '<div class="error-notice">
                            <div class="oaerror danger">
                            <strong>Uh oh!</strong> - Last Name must contain only alphabets and space.
                            </div>';

    }

    if(!filter_var($email,FILTER_VALIDATE_EMAIL)) {
        $error = true;
        $email_error = '<div class="error-notice">
                            <div class="oaerror danger">
                            <strong>Uh oh!</strong> - Please Enter Valid E-mail.
                            </div>';
    }
    if(strlen($password) < 6) {
        $error = true;
        $password_error = '<div class="error-notice">
                            <div class="oaerror danger">
                            <strong>Uh oh!</strong> - Password must be minimum of 6 characters.
                            </div>';
    }
    if($password != $cpassword) {
        $error = true;
        $cpassword_error = '<div class="error-notice">
                            <div class="oaerror danger">
                            <strong>Uh oh!</strong> - Make sure your passwords match.
                            </div>';

    }
    if (!$error) {
        if(mysqli_query($con, "INSERT INTO users(first_name,last_name,username,email,password,quote,who) VALUES('" . $first_name . "', '" . $last_name . "', '" . $username . "', '" . $email . "', '" . md5($password) . "', '" . $quote . "', '" . $who . "')")) {
            $successmsg = '<div class="error-notice">
                            <div class="oaerror success">
                            <strong>Wooh!</strong> - Successfully Registered! <a href="login.php">Click here to Login</a>
                            </div>';

        } else {
            $errormsg = '<div class="error-notice">
                            <div class="oaerror info">
                            <strong>Hmm.</strong> - Error in registering...Please try again later.
                            </div>';


        }
    }
}
?>

我在这里的代码末尾收到错误。 Error in registering...Please try again later.我不确定发生了什么。

Answer 1

为什么不检查$ _POST [＆＃34;用户名＆＃34;]的值是否在数据库中而不是与$ row进行比较？

即：

$con = mysqli_connect("localhost", "root", "", "testdb") or die("Error " . mysqli_error($con));

$usr = $_POST["username"];

$result = mysqli_query($con, "SELECT * FROM users WHERE username = '$usr'");
if (mysqli_fetch_array($result) > 0) {
$error = true;
$username_error = "Username is already in use.";
 }
}

如果用户名已经在数据库中，这将计算在内！

这是检查数据库中已存在的用户名的正确方法吗？如果没有，怎么样？

1 个答案: