下列常量由此扩展定义，且仅在此扩展编译入 PHP 或在运行时动态载入时可用。
FDFValue
(int)
FDFStatus
(int)
FDFFile
(int)
FDFID
(int)
FDFFf
(int)
FDFSetFf
(int)
FDFClearFf
(int)
FDFFlags
(int)
FDFSetF
(int)
FDFClrF
(int)
FDFAP
(int)
FDFAS
(int)
FDFAction
(int)
FDFAA
(int)
FDFAPRef
(int)
FDFIF
(int)
FDFEnter
(int)
FDFExit
(int)
FDFDown
(int)
FDFUp
(int)
FDFFormat
(int)
FDFValidate
(int)
FDFKeystroke
(int)
FDFCalculate
(int)
FDFNormalAP
(int)
FDFRolloverAP
(int)
FDFDownAP
(int)