解决 PHPMailer 附件发送失败：文件生成与邮件发送时序问题

<?php
// ... PHPMailer 类引入和设置 ...

if (isset($_POST['generate'])) {
    // PHPMailer 实例创建和SMTP设置
    // ...
    $mail->addAddress($_POST['customeremail']);
    // PHPMailer 尝试添加附件
    $mail->AddAttachment(dirname(__FILE__)."/CSD-Certificates/saved-certs/destruction-cert($customerref-$date).png");
    // ...
    $mail->send(); // 邮件发送
}

// ... HTML 表单 ...

// 证书生成逻辑（在PHPMailer代码块之后）
if (isset($_POST['generate'])) {
    // ... 证书图片生成代码 ...
    imagepng($createimage,$output,3); // 保存证书文件
}
?>

<?php
// ... PHPMailer 类引入和设置 ...

if (isset($_POST['generate'])) {
    $name = ucwords($_POST['name']);
    $customerref = ($_POST['customerref']);
    $date = ($_POST['date']);
    $customeremail = ($_POST['customeremail']);
    $weight = ucwords($_POST['weight']);

    // 1. 数据验证（建议放在最前面）
    if ($name == "" || $weight == "" || $date == "" || $customeremail == "" || $customerref == "") {
        echo "<div class='alert alert-danger col-sm-6' role='alert'>Not all form fields have been filled in. Please try again.</div>";
    } else {
        // 2. 证书生成逻辑：确保文件先被创建和保存
        $image = "CSD-Certificates/certi.png";
        $createimage = imagecreatefrompng($image);
        $output = "CSD-Certificates/saved-certs/destruction-cert($customerref-$date).png";

        // ... 证书文本和字体设置 ...
        // imagettftext(...)

        imagepng($createimage, $output, 3); // 核心：在这里保存证书文件

        // 3. PHPMailer 邮件发送逻辑：在文件生成之后执行
        $mail = new PHPMailer(true);
        try {
            // Server settings
            $mail->isSMTP();
            $mail->Host       = 'mail.smtp2go.com';
            $mail->SMTPAuth   = true;
            $mail->Username   = 'refurbsa.com';
            $mail->Password   = 'Y2F6ejMxbGFseTUw';
            $mail->SMTPSecure = PHPMailer::ENCRYPTION_SMTPS;
            $mail->Port       = 465;

            // Recipients
            $mail->setFrom('sender@example.com', 'Electronic Cemetery');
            $mail->addAddress($customeremail); // 使用已验证的变量
            $mail->addReplyTo('reply@example.com', 'Electronic Cemetery');

            // 添加附件：现在文件已经存在
            $mail->AddAttachment($output);

            // Content
            $mail->isHTML(true);
            $mail->Subject = 'Your E-Waste Disposal Certificate';
            $mail->Body    = "Good day $name,<br><br>..."; // 使用已验证的变量

            $mail->send();
            echo "<div class='alert alert-success col-sm-6' role='alert'>Congratulations! The certificate for $name has been generated and sent to $customeremail.</div>";
        } catch (Exception $e) {
            echo "Message could not be sent. Mailer Error: {$mail->ErrorInfo}";
        }
    }
}
?>