在PHP中实现验证码功能，通常需要以下几个步骤：
下面是一个简单的示例：
captcha.php的文件，用于生成验证码图片：<?php session_start(); // 生成一个随机的验证码 function generateRandomCaptcha() { $characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'; $charactersLength = strlen($characters); $randomCaptcha = ''; for ($i = 0; $i < 6; $i++) { $randomCaptcha .= $characters[rand(0, $charactersLength - 1)]; } return $randomCaptcha; } // 创建一个图像资源 $image = imagecreatetruecolor(120, 40); $backgroundColor = imagecolorallocate($image, 255, 255, 255); $textColor = imagecolorallocate($image, 0, 0, 0); imagefilledrectangle($image, 0, 0, 120, 40, $backgroundColor); // 在图像上添加随机文本 $captcha = generateRandomCaptcha(); imagettftext($image, 20, 0, 15, 30, $textColor, 'arial.ttf', $captcha); // 将图像保存到Session中 $_SESSION['captcha'] = $captcha; // 输出图像 header('Content-type: image/png'); imagepng($image); imagedestroy($image); ?> login.php，调用captcha.php生成验证码图片：<!DOCTYPE html> <html> <head> <title>登录</title> </head> <body> <h1>登录</h1> <form action="login.php" method="post"> <label for="username">用户名：</label> <input type="text" name="username" required> <br> <label for="password">密码：</label> <input type="password" name="password" required> <br> <label for="captcha">验证码：</label> <img src="captcha.php" alt="验证码" id="captcha"> <br> <input type="text" name="captcha" required> <br> <input type="submit" value="登录"> </form> </body> </html> login.php中验证用户输入的验证码是否正确：<?php session_start(); if ($_SERVER['REQUEST_METHOD'] == 'POST') { $username = $_POST['username']; $password = $_POST['password']; $userCaptcha = $_POST['captcha']; if ($userCaptcha == $_SESSION['captcha']) { // 验证码正确，进行登录操作 echo "登录成功！"; } else { // 验证码错误 echo "验证码错误，请重新输入！"; } } ?> 这样，一个简单的PHP验证码功能就实现了。你可以根据需要对代码进行调整和优化。
