PHP邮件程序脚本错误

我有一个提交页面，客户可以使用附带的mailer脚本扫描提交一个可填写的PDF表单和一张照片。表单正确上传到服务器，但是当它被发送到客户端时，PDF是空白的。

<?php
// did files get sent
if(isset($_FILES) && (bool) $_FILES) {
  // define allowed extensions
  $allowedExtensions = array("pdf","doc","docx","gif","jpeg","jpg","png","rtf","txt");
  $files = array();
  // loop through all the files
  foreach($_FILES as $name=>$file) {
     // define some variables
     $file_name = $file['name']; 
     $temp_name = $file['tmp_name'];
     // check if this file type is allowed
     $path_parts = pathinfo($file_name);
     $ext = $path_parts['extension'];
     if(!in_array($ext,$allowedExtensions)) {
        die("extension not allowed");
     }
     // move this file to the server YOU HAVE TO DO THIS
     $server_file = "/home/castmeb1/public_html/uploads/$path_parts[basename]";
     move_uploaded_file($temp_name,$server_file);
     // add this file to the array of files
     array_push($files,$server_file);
  }  
  // define some mail variables
  $to = "castmebg@gmail.com";
  $from = "castmebg@gmail.com"; 
  $subject ="test attachment"; 
  $msg = "Please see attached";
  $headers = "From: $from";
  // define our boundary
  $semi_rand = md5(time()); 
  $mime_boundary = "==Multipart_Boundary_x{$semi_rand}x";
  // tell the header about the boundary
  $headers .= "'nMIME-Version: 1.0'n";
  $headers .= "Content-Type: multipart/mixed;'n";
  $headers .= " boundary='"{$mime_boundary}'""; 
  // part 1: define the plain text email
  $message ="'n'n--{$mime_boundary}'n";
  $message .="Content-Type: text/plain; charset='"iso-8859-1'"'n";
  $message .="Content-Transfer-Encoding: 7bit'n'n" . $msg . "'n'n";
  $message .= "--{$mime_boundary}'n";
  // part 2: loop and define mail attachments
  foreach($files as $file) {
     $aFile = fopen($file,"rb");
     $data = fread($aFile,filesize($file));
     fclose($aFile);
     $data = chunk_split(base64_encode($data));
     $message .= "Content-Type: {'"application/octet-stream'"};'n";
     $message .= " name='"$file'"'n";
     $message .= "Content-Disposition: attachment;'n";
     $message .= " filename='"$file'"'n";
     $message .= "Content-Transfer-Encoding: base64'n'n" . $data . "'n'n";
     $message .= "--{$mime_boundary}'n";
  }
  // send the email
  $ok = mail($to, $subject, $message, $headers); 
  if ($ok) { 
     echo "<p>mail sent to $to!</p>"; 
  } else { 
     echo "<p>mail could not be sent!</p>"; 
  }
  die();
}
?>

谢谢，

JB