PHP发送带PDF附件邮件时MIME边界被识别为正文问题

你的代码存在几个MIME格式的关键错误，导致邮件客户端无法正确解析边界和附件，以下是问题点和修正方案：

问题分析 #

• 换行符不统一：邮件MIME协议强制要求所有头部和正文的换行必须使用\r\n，你代码里混合使用了\n和\r\n，破坏了邮件结构。
• Content-Transfer-Encoding行格式错误：你把base64声明和编码后的文件内容直接拼接在一起，没有换行和分隔空行，客户端无法区分协议头和附件内容。
• 边界定义的格式问题：头部中boundary参数的换行和空格处理不规范，可能导致客户端无法识别边界字符串。

修正后的代码 #

$home = $_SERVER['DOCUMENT_ROOT'];
$hostUrl = 'https://my-domain.com';

$tmpName = $_FILES['file']['tmp_name'];
$result = time().'-'.substr(sha1(mt_rand()),0,10);
$target = "/uploaded-files/".$result.".pdf";
$filePath = $home.$target;
$fileUrl = $hostUrl.$target;
move_uploaded_file($tmpName, $filePath);

$textMsg = '<p>Hi! Kanayo Austin</p>';
$textMsg .= '<p>Your request to print your JAMB Result Slip was successful and below is a PDF attachment of your JAMB Result Slip.</p>';

$textMsg .= '<p>You can also login to your account to download your JAMB Result Slip<a href="https://my-domain.com/login/">Login</a></p>';
$textMsg .= '<p>Need to access more of our services? <a href="https://my-domain.com/">Access More</a></p>';
$subject = "JAMB Result Slip";
$templateUrl = $hostUrl.'/mail-templates/default.php?title='.urlencode($subject).'&text='.urlencode($textMsg);
$msg = file_get_contents($templateUrl, true);

$file = fopen($filePath, 'rb');
$fileContent = fread($file, filesize($filePath));
fclose($file);
$data = chunk_split(base64_encode($fileContent));
$separator = md5(time());
$mimeBoundary = "==Multipart_Boundary_x{$separator}x";

// 修正头部：统一换行符，规范boundary格式
$headers = "From: Grafil Computers <noreply@grafil-computers.com>\r\n";
$headers .= "MIME-Version: 1.0\r\n";
$headers .= "Content-Type: multipart/mixed; boundary=\"{$mimeBoundary}\"\r\n";

// 修正正文：所有换行用\r\n，修复Content-Transfer-Encoding行
$message = "--{$mimeBoundary}\r\n";
$message .= "Content-Type: text/html; charset=\"UTF-8\"\r\n";
$message .= "Content-Transfer-Encoding: 7bit\r\n\r\n";
$message .= $msg . "\r\n";
$message .= "--{$mimeBoundary}\r\n";
$message .= "Content-Type: application/pdf; name=\"Result-Slip.pdf\"\r\n";
$message .= "Content-Disposition: attachment; filename=\"Result-Slip.pdf\"\r\n";
$message .= "Content-Transfer-Encoding: base64\r\n\r\n";
$message .= $data . "\r\n";
$message .= "--{$mimeBoundary}--\r\n";

mail('name@email.com', $subject, $message, $headers);

关键修改说明 #

1. 统一换行符：所有头部和正文的换行全部替换为\r\n，严格符合MIME标准。
2. 修复附件编码行：将Content-Transfer-Encoding: base64和附件内容分开，中间添加\r\n\r\n作为分隔，让客户端能正确识别附件内容的起始位置。
3. 规范头部格式：调整Content-Type行的格式，去掉多余空格，确保boundary参数被正确解析。

内容的提问来源于stack exchange，提问作者KANAYO AUGUSTIN UG