PHPMailer 附件发送失败：文件生成与邮件发送时序问题解析

<?php
// ... 其他必要的引入和设置 ...

if (isset($_POST['generate'])) {
    // 1. 获取表单数据
    $name = ucwords($_POST['name']);
    $customerref = ($_POST['customerref']);
    $date = ($_POST['date']);
    $customeremail = ($_POST['customeremail']);
    $weight = ucwords($_POST['weight']);

    // 2. 数据验证
    if (empty($name) || empty($weight) || empty($date) || empty($customeremail) || empty($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 {
        // 3. 执行证书生成逻辑
        // 定义输出路径和文件名
        $outputFilePath = dirname(__FILE__) . "/CSD-Certificates/saved-certs/destruction-cert($customerref-$date).png";

        // 创建图片资源，添加文本等操作
        $image = "CSD-Certificates/certi.png";
        $createimage = imagecreatefrompng($image);
        // ... 其他图片处理代码 (字体、颜色、文本定位等) ...

        // 确保文件写入成功
        if (imagepng($createimage, $outputFilePath, 3)) {
            // 证书生成成功后，再进行邮件发送
            echo "<div class='alert alert-success col-sm-6' role='alert'>Congratulations! The certificate for $name has been generated and sent to $customeremail.</div>";

            // 4. PHPMailer 邮件发送逻辑
            $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 $customeremail 变量
                $mail->addReplyTo('replyto@example.com', 'Electronic Cemetery');

                // 添加附件，此时文件已确保存在并完成写入
                $mail->AddAttachment($outputFilePath);

                // Content
                $mail->isHTML(true);
                $mail->Subject = 'Your E-Waste Disposal Certificate';
                $mail->Body    = "Good day $name,<br><br>... (邮件正文)";

                $mail->send();
                // 邮件发送成功提示 (可选)
            } catch (Exception $e) {
                echo "Message could not be sent. Mailer Error: {$mail->ErrorInfo}";
            }
        } else {
            echo "<div class='alert alert-danger col-sm-6' role='alert'>Error generating certificate.</div>";
        }
        // 销毁图片资源
        imagedestroy($createimage);
    }
}
?>