解决 PHPMailer 附件发送失败：文件生成与邮件发送的时序问题

<?php
include 'settings.php'; // 包含设置文件

// 导入 PHPMailer 类
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\SMTP;
use PHPMailer\PHPMailer\Exception;

// 加载 Composer 的自动加载器或手动引入文件
require 'PHPMailer-master/src/PHPMailer.php';
require 'PHPMailer-master/src/SMTP.php';
require 'PHPMailer-master/src/Exception.php';

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

    // 输入验证
    if (empty($name) || empty($weight) || empty($date) || empty($customeremail) || empty($customerref)) {
        echo "<div class='alert alert-danger col-sm-6' role='alert'>并非所有表单字段都已填写。请重试。</div>";
    } else {
        // --------------------------------------------------------
        // 第一步：生成并保存证书文件
        // --------------------------------------------------------
        $image = "CSD-Certificates/certi.png";
        $createimage = imagecreatefrompng($image);
        $output = dirname(__FILE__)."/CSD-Certificates/saved-certs/destruction-cert($customerref-$date).png"; // 确保使用完整路径

        // 颜色定义
        $white = imagecolorallocate($createimage, 254, 254, 254);
        $black = imagecolorallocate($createimage, 0, 0, 0);
        $rotation = 0;
        $drFont = "CSD-Certificates/TitilliumWeb-Regular.ttf";

        // 根据名称长度调整字体大小和位置 (此处省略了完整的逻辑，仅作示意)
        $name_len = strlen($name);
        $font_size = 50; // 示例值
        $origin_x = 1600; // 示例值
        $origin_y = 700; // 示例值

        // 在图片上绘制文本
        imagettftext($createimage, $font_size, $rotation, $origin_x, $origin_y, $white, $drFont, $name);
        imagettftext($createimage, 50, $rotation, 2300, 900, $white, $drFont, $weight);
        imagettftext($createimage, $font_size, $rotation, 1850, 900, $white, $drFont, $date);
        imagettftext($createimage, $font_size, $rotation, 2200, 1980, $white, $drFont, $date);
        imagettftext($createimage, $font_size, $rotation, 2200, 2180, $white, $drFont, $customerref);

        // 将图片保存到文件系统
        imagepng($createimage, $output, 3);
        imagedestroy($createimage); // 释放内存

        // --------------------------------------------------------
        // 第二步：发送邮件（在证书文件保存后执行）
        // --------------------------------------------------------
        $mail = new PHPMailer(true); // 启用异常

        try {
            // 服务器设置
            $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;

            // 收件人
            $mail->setFrom('sender@example.com', 'Electronic Cemetery');
            $mail->addAddress($customeremail);
            $mail->addReplyTo('replyto@example.com', 'Electronic Cemetery');

            // 添加附件 (现在文件应该已经存在了)
            $mail->AddAttachment($output); // 使用之前保存文件的完整路径

            // 内容
            $mail->isHTML(true);
            $mail->Subject = 'Your E-Waste Disposal Certificate';
            $mail->Body    = "Good day $name,<br><br>
Thank you very much for making use of our services. Your collection has been processed and I have attached your destruction certificate to this email.  
<br><br>
If you were happy with our service then it would be very much appreciated if you would spare a moment to give us your review <a href='https://www.facebook.com/eastcoastewaste/reviews'>HERE</a>
<br><br>
We look forward to assisting you with all your e-Waste needs in the future.
<br><br>
Wishing you a wonderful day further!
<br><br>
The Electronic Cemetery Team";

            $mail->send();
            echo "<div class='alert alert-success col-sm-6' role='alert'>恭喜！$name 的证书已生成并发送到 $customeremail。</div>";

        } catch (Exception $e) {
            echo "消息无法发送。邮件错误：{$mail->ErrorInfo}";
        }
    }
}
?>