PHP Manual: Set the value of a field

bool fdf_set_value(
    resource $fdf_document,
    string $fieldname,
    mixed $value,
    int $isName = ?
)

Sets the value for the given field.

fdf_document: The FDF document handle, returned by fdf_create, fdf_open or fdf_open_string.
fieldname: Name of the FDF field, as a string.
value: This parameter will be stored as a string unless it is an array. In this case all array elements will be stored as a value array.
isName: Note:
In older versions of the FDF toolkit last parameter determined if the field value was to be converted to a PDF Name (= 1) or set to a PDF String (= 0).

The value is no longer used in the current toolkit version 5.0. For compatibility reasons it is still supported as an optional parameter, but ignored internally.

Returns true on success or false on failure.

fdf_set_value