创建HTML/PHP格式的电子邮件表单，并在电子邮件中包含下拉选择、消息区和附件

<form action="submit.php" method="post" enctype="multipart/form-data">
  <!-- 表单内容 -->
</form>

<select name="dropdown">
  <option value="option1">选项1</option>
  <option value="option2">选项2</option>
  <option value="option3">选项3</option>
</select>

<textarea name="message" rows="4" cols="50"></textarea>

<input type="file" name="attachment">

<?php
$dropdown = $_POST['dropdown'];
$message = $_POST['message'];
$attachment = $_FILES['attachment'];

// 处理表单数据和文件

// 发送电子邮件
$to = 'recipient@example.com';
$subject = '邮件主题';
$headers = 'From: sender@example.com' . "\r\n";
$headers .= 'Content-Type: text/html; charset=UTF-8' . "\r\n";

// 构建邮件内容
$body = '<p>下拉选择: ' . $dropdown . '</p>';
$body .= '<p>消息区: ' . $message . '</p>';

// 处理附件
if ($attachment['error'] == UPLOAD_ERR_OK) {
  $tmp_name = $attachment['tmp_name'];
  $name = $attachment['name'];
  move_uploaded_file($tmp_name, 'uploads/' . $name);
  $attachment_path = 'uploads/' . $name;

  // 添加附件到邮件
  $file_content = file_get_contents($attachment_path);
  $file_encoded = base64_encode($file_content);
  $body .= '<p>附件: <a href="data:application/octet-stream;base64,' . $file_encoded . '">' . $name . '</a></p>';
}

// 发送邮件
mail($to, $subject, $body, $headers);
?>