(PHP 4, PHP 5)
fdf_set_ap — Set the appearance of a field
$fdf_document
   , string $field_name
   , int $face
   , string $filename
   , int $page_number
   )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
     
   成功时返回 TRUE, 或者在失败时返回 FALSE。