人们注册时如何防止重复用户名？

Question

我一直在做一个登录/注册系统，我正在接近完成我的注册部分代码。我遇到的唯一问题是如何使它使用户不能用重复的用户名注册。我想让它工作，使我的数据库不会接受信息，它会告诉用户有关错误。

我的PHP

<?php

include 'database_connection.php';
if (isset($_POST['formsubmitted'])) {
    $error = array(); //Declare An Array to store any error message
if (empty($_POST['name'])) {//if no name has been supplied
    $error[] = 'Please Enter a name '; //add to array "error"
} else {
    $name = $_POST['name']; //else assign it a variable
}

    if (empty($_POST['e-mail'])) {
        $error[] = 'Please Enter your Email ';
    } else {
        if (preg_match("/^([a-zA-Z0-9])+([a-zA-Z0-9\._-])*@([a-zA-Z0-9_-])+([a-zA-Z0-9\._-]+)+$/", $_POST['e-mail'])) {
            //regular expression for email validation
            $Email = $_POST['e-mail'];
        } else {
            $error[] = 'Your EMail Address is invalid  ';
        }
    }

    if (empty($_POST['Password'])) {
        $error[] = 'Please Enter Your Password ';
    } else {
        $Password = $_POST['Password'];
    }

    if (empty($error)) {
        //send to Database if there's no error '
    }
}

Answer 1

防止数据库中重复用户名的最佳方法是使数据库列成为主键或将其标记为唯一。

-- Make it a primary key
ALTER TABLE users ADD PRIMARY KEY(username);
-- or set it to be unique
ALTER TABLE users ADD UNIQUE (username);

这将防止表中有相同用户名的重复记录。当您尝试插入相同的一个时，将生成一个错误。

然后可以在PHP中捕获异常并检查原因。重复约束SQL错误代码为1062。

下面是使用PDO时如何捕获此错误的示例：

$error = [];
$username = 'Dharman';

$pdo = new \PDO("mysql:host=localhost;dbname=test;charset=utf8mb4", 'user', 'password', [
    \PDO::ATTR_ERRMODE => \PDO::ERRMODE_EXCEPTION,  // make sure the error reporting is enabled!
    \PDO::ATTR_EMULATE_PREPARES => false
]);

try {
    $stmt = $pdo->prepare('INSERT INTO users(username) VALUE(?)');
    $stmt->execute([$username]);
} catch (\PDOException $e) {
    if ($e->errorInfo[1] === 1062) {
        $error[] = "This username is already taken!";
    }
}

下面是使用Mysqli时如何捕获此错误的示例：

$error = [];
$username = 'Dharman';

// make sure the error reporting is enabled!
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$mysqli = new mysqli('localhost', 'user', 'password', 'test');
$mysqli->set_charset('utf8mb4');

try {
    $stmt = $mysqli->prepare('INSERT INTO users(username) VALUE(?)');
    $stmt->bind_param('s', $username);
    $stmt->execute();
} catch (\mysqli_sql_exception $e) {
    if ($e->getCode() === 1062) {
        $error[] = "This username is already taken!";
    }
}

Answer 2

您可以这样做，例如，当用户发布用户名并单击submit时，您可以编写此代码或将其添加到您的代码中，并进行修改：

<?php

$connect = mysql_connect('whatever', 'whatever', 'whatever');
$database = mysql_select_db('your dbname');
$username = $_POST['username'];
if (isset($username)) {
    $mysql_get_users = mysql_query("SELECT * FROM table_name where username='$username'");

    $get_rows = mysql_affected_rows($connect);

    if ($get_rows >= 1) {
        echo "user exists";
        die();
    } else {
        echo "user do not exists";
    }
}