(PHP 4 >= 4.2.0, PHP 5 <= 5.0.5, PHP 7)
dio_write — Writes data to fd with optional truncation at length
$fd
   , string $data
   [, int $len = 0
  ] )
   dio_write() writes up to len 
   bytes from data to file fd. 
  
fdThe file descriptor returned by dio_open().
dataThe written data.
lenThe length of data to write in bytes. If not specified, the function writes all the data to the specified file.
   Returns the number of bytes written to fd.