(PHP 3 >= 3.0.6, PHP 4, PHP 5)
Saves a FDF document.
fdf_document
The FDF document handle, returned by fdf_create(), fdf_open() or fdf_open_string().
filename
If provided, the resulting FDF will be written in this parameter. Otherwise, this function will write the FDF to the default PHP output stream.
如果成功则返回 TRUE，失败则返回 FALSE。