Use PHP function 'mysqli_real_escape_string' to escape special characters in strings to avoid SQL injection

Use the PHP function "mysqli_real_escape_string" to escape special characters in the string to avoid SQL injection

Introduction: In the process of website development that interacts with the database, we often need to store the data entered by the user into the database. However, if the data entered by the user is not processed, a malicious user may use the entered data to conduct SQL injection attacks, causing serious damage to the database. In order to avoid this situation, we can use the PHP function "mysqli_real_escape_string" to escape the data entered by the user to ensure that the entered string will not be misunderstood as SQL code.

SQL injection: SQL injection is an attack method that maliciously exploits vulnerabilities in web applications. Attackers modify or steal database information by inserting SQL code into the input data. This is a common attack method that can lead to data leakage, database corruption, or even directly compromise the entire application.

Solution: In order to prevent SQL injection attacks, we can use the "mysqli_real_escape_string" function in PHP to escape user-entered data. This function handles special characters in the data to ensure that they are not mistaken for SQL codes, but only treated as ordinary strings.

Sample code:

<?php
// 连接到数据库
$mysqli = new mysqli("localhost", "root", "", "mydatabase");

// 检查连接是否成功
if ($mysqli->connect_errno) {
    echo "连接失败：" . $mysqli->connect_error;
    exit();
}

// 获取用户输入
$username = $_POST['username'];
$password = $_POST['password'];

// 对用户输入进行转义
$username = mysqli_real_escape_string($mysqli, $username);
$password = mysqli_real_escape_string($mysqli, $password);

// 构建SQL查询语句
$query = "SELECT * FROM users WHERE username='$username' AND password='$password'";

// 执行查询
$result = $mysqli->query($query);

// 检查查询结果
if ($result->num_rows > 0) {
    // 登录成功
    echo "登录成功！";
} else {
    // 登录失败
    echo "用户名或密码不正确！";
}

// 关闭数据库连接
$mysqli->close();
?>

In the above code, we first create a connection to the database and check whether the connection is successful. We then take the username and password entered by the user and escape them using the "mysqli_real_escape_string" function. Next, we construct a SQL query statement and execute the query. Finally, we check the query results, and if there is a matching user, the login is considered successful, otherwise the login is considered failed.

Summary: To prevent SQL injection attacks, we should always escape user-entered data. PHP provides the "mysqli_real_escape_string" function to help us accomplish this task. By using this function, we can ensure that the data entered by the user will not be misunderstood as SQL code, thereby effectively protecting the security of the database. It is strongly recommended to use this function in website development that interacts with the database to reduce potential security risks.

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