(PECL eio >= 0.0.1dev)
eio_write — Write to file
$fd
   , string $str
   [, int $length = 0
   [, int $offset = 0
   [, int $pri = EIO_PRI_DEFAULT
   [, callable $callback = NULL
   [, mixed $data = NULL
  ]]]]] )
  eio_write() writes up to length
  bytes from str at offset
  offset from the beginning of the file.
  
fdStream, Socket resource, or numeric file descriptor, e.g. returned by eio_open()
strSource string
lengthMaximum number of bytes to write.
offsetOffset from the beginning of file.
priThe request priority: EIO_PRI_DEFAULT, EIO_PRI_MIN, EIO_PRI_MAX, or NULL.
If NULL passed, pri internally is set to
EIO_PRI_DEFAULT.
callback
callback function is called when the request is done.
It should match the following prototype: 
void callback(mixed $data, int $result[, resource $req]);
datais custom data passed to the request.
resultrequest-specific result value; basically, the value returned by corresponding system call.
reqis optional request resource which can be used with functions like eio_get_last_error()
data
     Arbitrary variable passed to callback.
     
   eio_write() returns request resource on success or FALSE on error.