How to verify user input in PHP forms and improve security

With the popularity of the Internet, more and more websites require users to log in, register, query and other operations, which requires the use of PHP forms. However, when using PHP forms, security issues need to be taken into consideration. In order to improve the security of the website, we need to verify the content entered by the user. This article will introduce how to verify user input in PHP forms to improve website security.

1. Filter user input data

The first step is to filter user input data. There are many unnecessary characters in user input data, such as spaces, tabs, carriage returns, line feeds, etc. These characters may cause the PHP script to fail to execute or be exploited by attackers. Therefore, we need to use functions in PHP to filter these characters.

The strip_tags() function in PHP can filter out HTML and PHP tags and return the filtered string. For example:

$username = strip_tags($_POST['username']); // 过滤掉HTML和PHP标签

The trim() function in PHP can filter out excess spaces, tabs, carriage returns, and line feeds at both ends of a string. For example:

$username = trim($_POST['username']); // 过滤掉两端空格、制表符、回车和换行符

2. Verify user input data

The second step is to verify user input data. We can use regular expressions in PHP to verify user-entered data. Regular expression is an expression used to match strings and can be used to check whether the data entered by the user meets the requirements.

Verify mobile phone number:

$phone = $_POST['phone'];
if(!preg_match('/^1[3|4|5|7|8][0-9]{9}$/', $phone)){ // 使用正则表达式进行校验
    echo '手机号码格式不正确';
}

Verify email address:

$email = $_POST['email'];
if(!preg_match('/^[a-zA-Z0-9]+@[a-zA-Z0-9]+.[a-zA-Z]+$/', $email)){ // 使用正则表达式进行校验
    echo '邮箱格式不正确';
}

3. Prevent SQL injection attacks

The third step is to prevent SQL injection attacks . SQL injection attack is a common attack method. Attackers can damage the database or even steal data by injecting malicious code into SQL statements. Therefore, in PHP forms, we need to use some functions to filter the data entered by the user.

The mysqli_real_escape_string() function in PHP can escape special characters such as single quotes, double quotes, backslashes, etc. in the string input by the user to avoid SQL injection attacks. For example:

$username = mysqli_real_escape_string($conn, $_POST['username']); // 过滤掉单引号、双引号、反斜线等特殊字符

4. Use verification code

Finally, in order to prevent malicious attacks, we can use verification code. Verification code is a human-machine identification technology that can prevent robots or malicious programs from maliciously attacking the website. We can add verification code function to PHP form to verify user input.

PHP verification code generation function:

$code = '';
for($i = 0; $i < 4; $i++){
    $code .= rand(0, 9); // 生成四位随机验证码
}
$img = imagecreatetruecolor(80, 30); // 创建图片
$bg_color = imagecolorallocate($img, 255, 255, 255); // 设置背景颜色
$font_color = imagecolorallocate($img, 0, 0, 0); // 设置字体颜色
imagefill($img, 0, 0, $bg_color); // 填充背景颜色
imagettftext($img, 18, 0, 10, 20, $font_color, 'arial.ttf', $code); // 添加文本
header('Content-Type:image/png'); // 设置图像类型
imagepng($img); // 输出图像
imagedestroy($img); // 销毁图片

PHP verification code verification:

$code = $_POST['code'];
if($code != $_SESSION['code']){ // 判断验证码是否匹配
    echo '验证码不正确';
}

Summary:

By filtering user input data and verifying user input data , preventing SQL injection attacks, using verification codes and other measures can improve the security in PHP forms to a relatively high level. When using PHP forms, we need to pay attention to security issues and update website programs in a timely manner to prevent hacker attacks.

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