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Home Backend Development PHP Tutorial How to generate refreshable image verification code using PHP

How to generate refreshable image verification code using PHP

Sep 13, 2023 am 11:54 AM
php generate Image verification code

How to generate refreshable image verification code using PHP

How to use PHP to generate a refreshable image verification code

With the development of the Internet, in order to prevent malicious attacks and automatic machine operations, many websites use verification code for user authentication. One common type of verification code is the image verification code, which generates a picture containing random characters and requires the user to enter the correct characters before proceeding.

This article will introduce how to use PHP to generate refreshable image verification codes and provide specific code examples.

Step 1: Create a verification code image

First, we need to create a function for generating a verification code image. Through PHP's GD library, we can easily manipulate images. The following is a sample code for creating a verification code image:

<?php
function generateCaptcha($length = 6) {
    // 生成隨機的驗證碼字符串
    $chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
    $captcha = '';
    for ($i = 0; $i < $length; $i++) {
        $captcha .= $chars[rand(0, strlen($chars) - 1)];
    }

    // 將驗證碼字符串保存到Session中,以備后續(xù)驗證
    session_start();
    $_SESSION['captcha'] = $captcha;

    // 創(chuàng)建一個空白的驗證碼圖片
    $image = imagecreatetruecolor(120, 40);
    $background_color = imagecolorallocate($image, 255, 255, 255);
    imagefill($image, 0, 0, $background_color);

    // 在驗證碼圖片上繪制隨機的字符
    $text_color = imagecolorallocate($image, 0, 0, 0);
    imagettftext($image, 20, 0, 10, 30, $text_color, 'path/to/font.ttf', $captcha);

    // 輸出驗證碼圖片
    header('Content-type: image/png');
    imagepng($image);
    imagedestroy($image);
}
?>

In the above code, the generateCaptcha function is used to generate a verification code and save the verification code string to the Session. Then, create a blank verification code picture, set the background color, text color, font and other parameters, and draw the verification code on the picture. Finally, set the output content type to image through the header function, call the imagepng function to output the image, and then destroy the image resource.

Step 2: Use the verification code image

The following is a simple sample code for displaying the verification code image on the web page and accepting the verification code entered by the user:

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>生成驗證碼</title>
</head>
<body>
    <form action="verify_captcha.php" method="post">
        <label for="captcha">請輸入驗證碼:</label>
        <input type="text" id="captcha" name="captcha">
        <img src="/static/imghw/default1.png"  data-src="captcha.php"  class="lazy" alt="驗證碼">
        <button type="submit">提交</button>
    </form>
</body>
</html>

In the above code, the action attribute of the form form points to a PHP file that verifies the verification code (such as verify_captcha.php), img## The src attribute of the #tag points to the PHP file that generates the verification code image (such as captcha.php). After the user enters the verification code in the input box, the form is submitted and verified.

Step 3: Verify the entered verification code

Finally, we need to create a PHP file to verify whether the verification code entered by the user is correct. The following is a simple sample code for verifying the verification code:

<?php
session_start();

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $inputCaptcha = $_POST['captcha'];
    $captcha = $_SESSION['captcha'];

    if ($inputCaptcha === $captcha) {
        echo '驗證碼正確';
    } else {
        echo '驗證碼錯誤';
    }
}
?>
In the above code, the Session is first opened through the

session_start function, and then the verification code entered by the user and previously saved in the Session are obtained Verification codes are compared. If they are the same, output "verification code is correct"; if they are different, output "verification code is wrong".

The above are the steps and code examples for using PHP to generate refreshable image verification codes. In this way, we prevent automated machines from operating and increase the security of our websites and applications.

The above is the detailed content of How to generate refreshable image verification code using PHP. For more information, please follow other related articles on the PHP Chinese website!

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