如何防止再次注册进入系统

Question

我已经创建了一个注册表单，我希望防止同一个用户一次又一次地注册该系统。这是我的代码，请帮我解决这个问题。在初始注册时，只考虑用户名、密码和电子邮件，在登录系统后，用户可以更新姓名、性别、教育等信息：.

<?php
session_start();

include_once 'newFunctions.php';
include_once 'dbConnect.php';

// database connection
dbConnect(); 

$username = $_POST['username'];
$pw=md5($_POST['password']);
$email=$_POST['email'];

//check the term
if(isset($_POST['term'])){
    $is_checked = 1;
}else{
    $is_checked = 0;
}


$insert_data="INSERT INTO tutor(userName, password, email, avatar, term)
    VALUES
    ( '{$username}','{$pw}','{$email}','default_image.jpg','{$is_checked}')";


$check=mysql_query($insert_data);

if($check=='true')
{

// session variables
$_SESSION['login'] = "1";
$_SESSION['username']=$username; 
$_SESSION['password']=$pw;

showAlert("You Have Successfully Registered ", "../tutor_panel_ui.php");

}

else{

echo "Invalid Login";

$_SESSION['login'] = '';
}

?>

Answer 1

在此之前

 $insert_data="INSERT INTO tutor(userName, password, email, avatar, term)
VALUES
( '{$username}','{$pw}','{$email}','default_image.jpg','{$is_checked}')";

运行一个查询，以检查数据库中是否已经存在电子邮件id或/和用户名。

会是这样的

$query="SELECT userName (or/and) email FROM tutor WHERE email ='$email' (or/and) userName=$username ";

检查返回的结果是空的还是包含了一些行。如果是空的，继续注册用户，否则告诉用户他已经注册了，并且不能再次注册。

Answer 2

我要做的是:将家教专栏、电子邮件和用户名设置为UNIQUE KEY。然后我将对您的代码进行以下编辑：

<?php
session_start();

include_once 'newFunctions.php';
include_once 'dbConnect.php';

// database connection
dbConnect(); 

$username = $_POST['username'];
$pw=md5($_POST['password']);
$email=$_POST['email'];

//check the term
if(isset($_POST['term'])){
    $is_checked = 1;
}else{
    $is_checked = 0;
}


$insert_data="INSERT INTO tutor(userName, password, email, avatar, term)
    VALUES
    ( '".mysql_real_escape_string({$username})."','".mysql_real_escape_string({$pw})."','{".mysql_real_escape_string($email})."','default_image.jpg','{$is_checked}')";


$check=mysql_query($insert_data);

if($check=='true')
{

// session variables
$_SESSION['login'] = "1";
$_SESSION['username']=$username; 
$_SESSION['password']=$pw;

showAlert("You Have Successfully Registered ", "../tutor_panel_ui.php");
//showAlert is a javascript function - so unless you have defined it in your other files you'll need to do a different thing here.
}

else{

echo "Registration data invalid. Username and email must be unique. Are you already signed up and forgot your password? if so <a href='recoverpassword.php'>Recover your password</a>.";

$_SESSION['login'] = '';
}

?>

注意:我在其中添加了mysql_real_escape_string()调用，以避免可怕的致命的SQL注入风险，但是您应该考虑升级到PDO_或mysqli_，而不是mysql_函数。