The fdf_set_value() function sets the value for a field named fieldname. The value will be stored as a string unless it is an array. In this case all array elements will be stored as a value array.
In older versions of the fdf toolkit last parameter determined if the field value was to be converted to a PDF Name (isName = 1) or set to a PDF String (isName = 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 beginning with PHP 4.3, but ignored internally.
Support for value arrays was added in PHP 4.3.