variant_set_type — Convert a variant into another type "in-place"
This function is similar to variant_cast() except that the variant is modified "in-place"; no new variant is created. The parameters for this function have identical meaning to those of variant_cast().
Es wird kein Wert zurückgegeben.
In my application I was using ADODB to retrieve data from Microsoft Access. During queries, fields defined as "Date/Time" in Access were being returned to PHP as instances of the Variant class.
For some reason, the variant_date_to_timestamp function returned incorrect timestamps. As a workaround, I used variant_set_type($variant, VT_BSTR) to get a string representation of the date. This can be used for most variant types PHP doesn't handle.