only allow jpg and png file extensions phpmailer

[gw1500se]

That is what is in $_FILES['userfile']? If so then that means it contains an empty array (I didn't know it would do that). I suggest you change the logic a bit and check for errors. Remove the 'if' outside the 'foreach' and try this:

foreach($_FILES['userfile']['name'] as $name) {
   if ($name['error']==0) {
      /* handle file */
   }
   else {
      /* handle error */
   }
}

You will need to decide how to handle the errors. Oddly, I think code 4 means duplicate file names.