By creating an file, writing anything to the file pointer and uploading the file without rewinding the file pointer, ftp_fput sends about 40 bytes of data which I can't identify precisely. The following (useless) snippet causes the reproducible effect:

  $conn_id = ftp_connect ($host); 
  $login_result = ftp_login ($conn_id, $user,$pass); 
  $fp = tmpfile ();
  fputs ($fp, 'foobar');
  $upload = ftp_fput($conn_id, 'test', $fp, FTP_ASCII);

greetings, Keita