PHPMailer支持.doc/图片附件，PDF附件无法发送问题求助

Hey there! It looks like you're hitting a snag where PDF attachments won't send through your contact form, even though DOC files and images work perfectly. Let's walk through the most likely issues and how to fix them:

1. First, Capture Detailed Error Messages #

Your current code has error reporting commented out, which makes it impossible to pinpoint exactly why PDFs are failing. Start by enabling error logging and PHPMailer's debug output:

error_reporting(E_ALL);
ini_set('display_errors', 1);

Also, after attempting to move the uploaded file, add a quick check to verify the PDF isn't corrupted:

if (move_uploaded_file($_FILES['userfile']['tmp_name'], $uploadfile)) {
    // Verify the uploaded PDF is intact
    if (!file_exists($uploadfile) || filesize($uploadfile) === 0) {
        echo "Uploaded PDF is corrupted or empty";
        exit;
    }
    // Rest of your PHPMailer code...
}

2. Add Proper File Upload Validation #

You're missing critical checks for file type and size, which could let through invalid PDFs (like files over 2MB) or files mislabeled as PDFs. Add this validation before handling the upload:

// Allowed file types (uses real file content MIME types, not client-reported values)
$allowedMimes = [
    'application/pdf',
    'application/msword',
    'image/jpeg',
    'image/png',
    'image/gif'
];
// Allowed file extensions
$allowedExts = ['pdf', 'doc', 'jpg', 'jpeg', 'png', 'gif'];
// 2MB size limit
$maxFileSize = 2 * 1024 * 1024;

$uploadedFile = $_FILES['userfile'];
$fileExtension = strtolower(pathinfo($uploadedFile['name'], PATHINFO_EXTENSION));
$fileMime = mime_content_type($uploadedFile['tmp_name']);

// Check file size
if ($uploadedFile['size'] > $maxFileSize) {
    echo "File exceeds 2MB limit";
    exit;
}
// Double-validate extension and MIME type for security
if (!in_array($fileExtension, $allowedExts) || !in_array($fileMime, $allowedMimes)) {
    echo "Only .doc, .pdf, and image files are allowed";
    exit;
}

Using mime_content_type ensures you're checking the actual file content, not just the filename or client-reported MIME type (which can be faked).

3. Fix PHPMailer's AddAttachment Call #

Your current AddAttachment syntax has a small issue—you shouldn't declare the $encoding variable inside the function call. Also, explicitly specifying the PDF's MIME type helps mail clients and servers recognize the attachment correctly:

// Get the actual MIME type of the uploaded file
$attachmentMime = mime_content_type($uploadfile);
// Add the attachment with correct encoding and MIME type
$mail->AddAttachment($uploadfile, $uploadedFile['name'], 'base64', $attachmentMime);

This ensures PHPMailer handles the PDF's encoding properly, which is often the culprit when PDFs fail to send but other files work.

4. Check Server and Gmail SMTP Settings #

• Server Upload Limits: Make sure your PHP config (php.ini) has upload_max_filesize and post_max_size set to at least 2MB (or higher if needed).
• Gmail SMTP Requirements: If you're using Gmail, ensure:
  • You've enabled "Less secure app access" (if you haven't set up 2FA).
  • If you have 2FA enabled, use an App Password instead of your regular account password.
  • Add SMTP debugging to see exactly what's happening with the connection:

    $mail->SMTPDebug = 2; // Outputs detailed SMTP logs (disable in production)
    $mail->Debugoutput = 'html';
    

    This will show you if Gmail is rejecting the PDF attachment for any reason.

Full Fixed Code Example #

<?php
error_reporting(E_ALL);
ini_set('display_errors', 1);
date_default_timezone_set('America/Toronto');
require_once('class.phpmailer.php');

$msg = '';
if (array_key_exists('userfile', $_FILES)) {
    // Upload Validation
    $allowedMimes = [
        'application/pdf',
        'application/msword',
        'image/jpeg',
        'image/png',
        'image/gif'
    ];
    $allowedExts = ['pdf', 'doc', 'jpg', 'jpeg', 'png', 'gif'];
    $maxFileSize = 2 * 1024 * 1024;

    $uploadedFile = $_FILES['userfile'];
    $fileExtension = strtolower(pathinfo($uploadedFile['name'], PATHINFO_EXTENSION));
    $fileMime = mime_content_type($uploadedFile['tmp_name']);

    if ($uploadedFile['size'] > $maxFileSize) {
        echo "File exceeds 2MB limit";
        exit;
    }
    if (!in_array($fileExtension, $allowedExts) || !in_array($fileMime, $allowedMimes)) {
        echo "Only .doc, .pdf, and image files are allowed";
        exit;
    }

    // Handle File Upload
    $uploadfile = tempnam(sys_get_temp_dir(), hash('sha256', $uploadedFile['name']));
    if (move_uploaded_file($uploadedFile['tmp_name'], $uploadfile)) {
        if (!file_exists($uploadfile) || filesize($uploadfile) === 0) {
            echo "Uploaded file is corrupted or empty";
            exit;
        }

        // Configure PHPMailer
        $mail = new PHPMailer;
        $mail->IsSMTP();
        $mail->SMTPAuth = true;
        $mail->SMTPSecure = 'tls';
        $mail->Host = "smtp.gmail.com";
        $mail->Port = 587;
        $mail->Username = "exampl@gmail.com";
        $mail->Password = 'your_app_password_or_account_password';
        // Uncomment for debugging:
        // $mail->SMTPDebug = 2;
        // $mail->Debugoutput = 'html';

        $name = $_POST['name'];
        $email = $_POST['email'];
        $message = "Name: ".($name)."\n";
        $message .= "Email: ".($email)."\n";
        $message .= "Message: ".$_POST['message'];

        $mail->addAddress("example@gmail.com");
        $mail->SetFrom($email, $name);
        $mail->Subject = "Message from website";
        $mail->Body = $message;

        // Add Attachment with Correct MIME Type
        $attachmentMime = mime_content_type($uploadfile);
        $mail->AddAttachment($uploadfile, $uploadedFile['name'], 'base64', $attachmentMime);

        if($mail->Send()) {
            echo "Message sent!";
            // Clean up temporary file
            unlink($uploadfile);
        } else {
            echo "Mailer Error: " . $mail->ErrorInfo;
            unlink($uploadfile);
        }
    } else {
        $msg = 'Failed to move file to ' . $uploadfile;
        echo $msg;
    }
}
?>

Final Notes #

• Always delete temporary files after sending the email (the code above uses unlink($uploadfile) to do this) to avoid filling up your server's disk space.
• Disable error reporting and SMTP debugging when deploying to production to protect sensitive information.
• If you're still having issues, check the PHPMailer error output—it will tell you exactly where the problem is (e.g., attachment encoding, SMTP authentication, etc.).

内容的提问来源于stack exchange，提问作者webdev