How to use PHP to generate a verification code image that supports Chinese characters

How to use PHP to generate a verification code image that supports Chinese characters

With the development of the Internet, verification codes have become a common security feature on websites and applications verification method. Most verification codes usually use English characters and numbers, but sometimes, we need to generate verification codes that support Chinese characters. The following will introduce how to use PHP to generate a verification code image that supports Chinese characters, and provide specific code examples.

Step 1: Prepare Chinese character set
To generate a verification code image that supports Chinese characters, you first need to prepare a Chinese character set. We can choose common Chinese character sets, such as common Chinese characters, traditional Chinese characters or all Chinese characters, depending on the needs. Here we take commonly used Chinese characters as an example, stored in an array.

<?php
$chineseChars = array('一', '二', '三', '四', '五', '六', '七', '八', '九', '十', 
                      '百', '千', '万', '亿', '天', '地', '王', '赵', '钱', '孙');
?>

Step 2: Generate a random verification code
In the process of generating the verification code, we need to randomly select a certain number of characters from the Chinese character set. Here we choose 3 characters as the verification code. The specific implementation is as follows:

<?php
$code = ''; // 验证码初始化为空

for ($i = 0; $i < 3; $i++) {
    $index = mt_rand(0, count($chineseChars) - 1);
    $code .= $chineseChars[$index];
}
?>

Step 3: Generate verification code image
We need to use the GD library to generate verification code images. First, we need to create a canvas and set its width, height, and background color. Then, we draw the verification code text on the canvas. Finally, output the generated verification code image to the browser or save it as a file. The specific code is as follows:

<?php
$width = 120; // 画布宽度
$height = 40; // 画布高度

// 创建画布
$image = imagecreate($width, $height);

// 设置背景颜色
$bgColor = imagecolorallocate($image, 255, 255, 255);

// 随机选择一种颜色作为验证码文字颜色
$textColor = imagecolorallocate($image, mt_rand(0, 150), mt_rand(0, 150), mt_rand(0, 150));

// 绘制验证码文字
$fontFile = 'path/to/chinese_font.ttf'; // 中文字体文件路径
imagettftext($image, 20, 0, 10, 30, $textColor, $fontFile, $code);

// 输出验证码图片到浏览器
header('Content-Type: image/png');
imagepng($image);
imagedestroy($image);
?>

In the above code, we use the imagettftext function to draw the verification code text. This function needs to specify parameters such as font file path, font size, text angle, starting coordinates, and text color.

Step 4: Use the verification code image
After generating the verification code image, we can display it on the registration, login or password retrieval page of the website or application. Users need to enter a verification code to verify. The verification code is as follows:

<?php
session_start();

// 存储验证码到Session
$_SESSION['captcha'] = $code;
?>

<form action="verify.php" method="post">
    <img src="captcha.php" alt="验证码">
    <input type="text" name="code" placeholder="请输入验证码">
    <button type="submit">提交</button>
</form>

In the above code, we store the verification code in $_SESSION for use in subsequent verification processes.

Summary
Using PHP to generate a verification code image that supports Chinese characters requires preparing a Chinese character set, generating a random verification code, using the GD library to generate a verification code image, and using the verification code image on the page for verification. Through the above steps, we can easily implement the verification code function that supports Chinese characters.

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