(PHP 3 >= 3.0.6, PHP 4, PHP 5)
Sets the appearance of a field (i.e. the value of the /AP key).
fdf_document
The FDF document handle, returned by fdf_create(), fdf_open() or fdf_open_string().
field_name
face
The possible values FDFNormalAP, FDFRolloverAP and FDFDownAP.
filename
page_number
如果成功则返回 TRUE,失败则返回 FALSE。