在PHP中實現驗證碼功能，通常需要以下幾個步驟：
下面是一個簡單的示例：
captcha.php的文件，用于生成驗證碼圖片：<?php
session_start();
// 生成一個隨機的驗證碼
function generateRandomCaptcha() {
$characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
$charactersLength = strlen($characters);
$randomCaptcha = '';
for ($i = 0; $i < 6; $i++) {
$randomCaptcha .= $characters[rand(0, $charactersLength - 1)];
}
return $randomCaptcha;
}
// 創建一個圖像資源
$image = imagecreatetruecolor(120, 40);
$backgroundColor = imagecolorallocate($image, 255, 255, 255);
$textColor = imagecolorallocate($image, 0, 0, 0);
imagefilledrectangle($image, 0, 0, 120, 40, $backgroundColor);
// 在圖像上添加隨機文本
$captcha = generateRandomCaptcha();
imagettftext($image, 20, 0, 15, 30, $textColor, 'arial.ttf', $captcha);
// 將圖像保存到Session中
$_SESSION['captcha'] = $captcha;
// 輸出圖像
header('Content-type: image/png');
imagepng($image);
imagedestroy($image);
?>
login.php，調用captcha.php生成驗證碼圖片：<!DOCTYPE html>
<html>
<head>
<title>登錄</title>
</head>
<body>
<h1>登錄</h1>
<form action="login.php" method="post">
<label for="username">用戶名：</label>
<input type="text" name="username" required>
<br>
<label for="password">密碼：</label>
<input type="password" name="password" required>
<br>
<label for="captcha">驗證碼：</label>
<img src="captcha.php" alt="驗證碼" id="captcha">
<br>
<input type="text" name="captcha" required>
<br>
<input type="submit" value="登錄">
</form>
</body>
</html>
login.php中驗證用戶輸入的驗證碼是否正確：<?php
session_start();
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
$username = $_POST['username'];
$password = $_POST['password'];
$userCaptcha = $_POST['captcha'];
if ($userCaptcha == $_SESSION['captcha']) {
// 驗證碼正確，進行登錄操作
echo "登錄成功！";
} else {
// 驗證碼錯誤
echo "驗證碼錯誤，請重新輸入！";
}
}
?>
這樣，一個簡單的PHP驗證碼功能就實現了。你可以根據需要對代碼進行調整和優化。
