如何用简单的PHP在邮件中附加一些文件

<?php
// 邮件信息
$to = 'recipient@example.com';
$subject = '附件邮件测试';
$message = '这是一封带附件的测试邮件';

// 附件文件路径
$attachment = '/path/to/attachment.pdf';

// 生成邮件头部信息
$boundary = md5(time());
$headers = "From: sender@example.com\r\n";
$headers .= "MIME-Version: 1.0\r\n";
$headers .= "Content-Type: multipart/mixed; boundary=\"$boundary\"\r\n";

// 生成邮件内容
$body = "--$boundary\r\n";
$body .= "Content-Type: text/plain; charset=UTF-8\r\n";
$body .= "Content-Transfer-Encoding: 7bit\r\n\r\n";
$body .= "$message\r\n\r\n";
$body .= "--$boundary\r\n";
$body .= "Content-Type: application/pdf; name=\"attachment.pdf\"\r\n";
$body .= "Content-Transfer-Encoding: base64\r\n";
$body .= "Content-Disposition: attachment; filename=\"attachment.pdf\"\r\n\r\n";
$body .= chunk_split(base64_encode(file_get_contents($attachment)));
$body .= "--$boundary--";

// 发送邮件
if (mail($to, $subject, $body, $headers)) {
    echo "邮件发送成功！";
} else {
    echo "邮件发送失败！";
}
?>