Why? We are quite happy if guys who update the code update the documentation (with respective version notes), as otherwise many times the doc update is forgotten. Those types will be available in 4.3, so the documentation is quite all right.

I also must add the point that it still includes PHP 3 related information, like developing extensions for PHP 3 or migrating to PHP 4. Our intention is to provide a single manual for all versions in use (including all OS variations). Although sometimes we have problems with this approach (eg. missing version info for newly added items) most of the time this scheme works quite well.

I disagree, at least in part, because some of this advance documentation does not indicate that the functionality is not yet available.  An example is the documentation for getimagesize which says:

Returns an array with 4 elements. Index 0 contains the width of the image in pixels. Index 1 contains the height. Index 2 is a flag indicating the type of the image: 1 = GIF, 2 = JPG, 3 = PNG, 4 = SWF, 5 = PSD, 6 = BMP, 7 = TIFF(intel byte order), 8 = TIFF(motorola byte order), 9 = JPC, 10 = JP2, 11 = JPX, 12 = JB2, 13 = SWC, 14 = IFF. These values correspond to the IMAGETYPE constants that were added in PHP 4.3. [...]

*Some* of those image types are available in 4.2 or earlier.  It reads as if *all* of them were added in 4.3.  I've spent a chunk of today testing with 4.2.2 to see which parts are currently present and which ones are not.