How to use PHP functions to generate and verify verification codes for user registration and login?

How to use PHP functions to generate and verify verification codes for user registration and login?

In the user registration and login pages of the website, in order to prevent batch registration and attacks by robots, it is usually necessary to add a verification code function. This article will introduce how to use PHP functions to generate and verify verification codes for user registration and login.

1. Verification code generation

First, we need to generate a random verification code image for the user to fill in. PHP provides the GD library and image processing functions, which can easily generate verification code images.

<?php
// 创建一个画布
$image = imagecreatetruecolor(100, 30);

// 设置画布背景色为白色
$bgColor = imagecolorallocate($image, 255, 255, 255);
imagefill($image, 0, 0, $bgColor);

// 随机生成四位数字验证码
$code = rand(1000, 9999);

// 将验证码保存到Session中，用于后续验证
session_start();
$_SESSION['code'] = $code;

// 将验证码绘制到画布上
$fontColor = imagecolorallocate($image, 0, 0, 0);
imagestring($image, 5, 25, 8, $code, $fontColor);

// 输出图片
header('Content-Type: image/png');
imagepng($image);

// 清除画布资源
imagedestroy($image);
?>

The above code creates a 100x30 canvas, generates a four-digit random digital verification code, and saves the verification code to the Session. Finally, draw the verification code onto the canvas and output the image in PNG format.

2. Verification code verification

When a user submits a registration or login request, it needs to be verified whether the verification code filled in by the user matches the generated verification code. We can verify by comparing the verification code saved in the Session with the verification code submitted by the user.

<?php
session_start();

// 获取用户提交的验证码
$enteredCode = $_POST['code'];

// 获取Session中保存的验证码
$generatedCode = $_SESSION['code'];

// 清除Session中保存的验证码
unset($_SESSION['code']);

// 比较用户提交的验证码和Session中保存的验证码
if ($enteredCode == $generatedCode) {
    // 验证码匹配，执行登录或注册逻辑
    // ...
} else {
    // 验证码不匹配，返回错误提示
    echo "验证码错误";
}
?>

The above code first obtains the verification code submitted by the user and the verification code saved in the Session, and then compares it. If the verification code matches, the login or registration logic can be executed; if the verification fails, the corresponding error prompt can be returned.

Through the above code examples, we can implement the verification code generation and verification functions for user registration and login pages. Of course, for a better user experience, we can also beautify the verification code and add a click-to-refresh function, etc. I hope this article will be helpful to developers who use PHP to implement verification code functions.

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