Would be good, but also a lot of effort for the doc team to audit the whole text.  I'm not even sure if DocBook has a way to version sections of text.

I imagine this could initially be done so that the version information that already exists in the current documentation would be automatically parsed, and then the remaining version information could be applied later. And the version checking could also be done by a community effort. 

I'm not familiar with the documentation system that the php.net docs use, but the version data that is already available there is pretty extensive (especially with PHP5 specific functions), and generally speaking in a format that could easily be automatically parsed from the documentation. 

And of course, good things often require some effort. :)

Consider yourself privileged ;-) DocBook is a beast, and we have 30 or so different languages to maintain!

It would be fairly simple to hide functions that are PHP 5 only, but in many cases we have features that differ by PHP version; these would be impossible to parse automatically without some kind of AI that understands English (and one for each of the other languages).

Well, hiding (or highlighting) PHP5 only functions alone would be a significant improvement. The functional differences between versions are less important to separate, because whether the functionality is the same or not the user is already reading the documentation for the function at that point. And of course, the function is available at least in some form regardless of the version. 

On the other hand, it's only annoying that the documentation for strpos() lists functions stripos() and strripos() in the "See also" part, since they are not available in any form in versions prior to PHP5.

Good idea :) It would be nice, if we could modify our presentation code (DSSSL and livedocs) to put a little [5] sign or something like that after all the function names that are supported in PHP 5 only. I mean if we have a <function>php5_magic_function</functoin> then the output would be php5_magic_function()[5] (with the [5] being some good looking image or a <sup>-ed text). This would not hide the functions but mark them in the manual occurances. Also it would be nice to do the same on the reference TOC pages (which is different rendering code). Anyone with interest to code this?

The code for <function> and the TOC in ref.pages is exactly the same, because the TOC returns:
<function>xpto_func</function> - $title

And then this is parsed by the format_function() function.

This won't be hard to implement. If we agree in the presentation style, I may implement this.

may I suggest a small version of the "version 5 in a circle" graphic we have on php.net right now.

This little graphic can live in the phpweb theme (but make a copy of it for the default livedocs theme too) as it is likely that different sites will want a different rendition of the version number. (remember to "cvs add -kb" the graphic)

Also, thinking forward, I'd like to make this kind of generic by highlighting functions of the latest major version.  We can achieve this by defining a LATEST_VERSION constant to have the value of 5; whenever a function is introduced in the LATEST_VERSION, we can pull in LATEST_VERSION . '.gif' as the graphic.

When we get closer to PHP 6, all we'd need to do then is add a version 6 graphic and increment LATEST_VERSION.

This bug is old :) Anyway, I don't think functions should ever be hidden. Highlighted, sure, but never hidden. Users should know they exist and usually these functions have examples for the older versions of PHP so viewing them is a benefit to all.

This bug is closed. LiveDocs already implements this and we've mostly stopped adding features to DSSSL. All hail LiveDocs!