Just curious. Can it be done? has it been?

I dunno. Potential armys of add-on developers who use python, ruby, newlisp, rebol, or whatever, but not php.

hm, this sounds good. I'll think about it.

There must be some way how to pass the API to another language. It would be slower but it is possible I guess.

I think it wouldn't be so complicated, just not so secure and fast. My first completely not tested thoughts:

One can make a addon which would contain subfolder scripts/ and do something like this:

$descriptorspec = array(
0 => array("pipe", "r"), // stdin
1 => array("pipe", "w"), // stdout
2 => array("pipe", "w") // stderr
);

$scripts_dir = $Configuration['EXTENSIONS_PATH'].$EXTENSION_NAME.'/scripts/';
foreach ( executables( $scripts_dir ) => $script) {
$process = process_open ($scripts_dir.$script, $descriptorspec, $pipes);

fwrite($pipes[0], serialize_context());
fclose($pipes[0]);

$stuff_to_unserialize = stream_get_contents($pipes[1]);
fclose($pipes[1]);

if (proc_close($process)) {
unserialize_context_and_delegates($stuff_to_unserialize)
}
}

where:
executables returns list of executable files in a given folder
serialize_context would parse Context to some serialized format with info if this is first call or delegate call
unserialize_context_and_delegates would read some serialized data where would be:
- what changed in Context
- what delegate calls what function
also it would create delegate functions and hook them.
Each created delegate would look like this:

function DelegateFor{$script}{$FunctionName} () {

// some initialization here

$process = process_open ($scripts_dir.$script, $descriptorspec, $pipes);

fwrite($pipes[0], serialize_context_and_delegates('$FunctionName'));
fclose($pipes[0]);

$stuff_to_unserialize = stream_get_contents($pipes[1]);
fclose($pipes[1]);

if (proc_close($process)) {
unserialize_context_and_delegates($stuff_to_unserialize)
}
}

where
serialize_context_and_delegates would prepare the Context as serialize_context() but also would add info, that this is a delegate call and which one

So it would call the external script when it is initialized and also when each delegate is called.

Then you can have script even in a bash script.

Also I got an idea that there in scripts might be only some interface scripts for each language you want to use and it would read the real scripts from other places.
It would be also possible to return another script name for a delegate calls, so you can split your add-on into more scripts and call only those you really need in the delegation.

These interface scripts would read the serialized input from stdin - status, if this is an initial call or delegate call, prepare $Context to the language specific type.
If it is a delegate call, it would call the delegate only, if initial call, then init function only.
It would also define ChangeContext function which would change anything in a context and it would also prepare the data to return concerning the changes in the context.
And it would also define Delegate function which would be called if you want to delegate any function in the script and prepare the serialized delegation info.
At the end it would pass the context and delegation serialized data and return an exit code.

You'd need to make sure your server allowed PHP scripts to perform those sorts of functions as well as ensuring that it had things like python or ruby. Also, stream_get_contents is a PHP 5 only function and Vanilla is written in PHP 4 to be as widely-accessible as possible.

Other than that, your version does seem less complicated but it is also slower and less secure than a CGI C++ wrapper for the whole of Vanilla. Even so, I'm quite interested, I might make a proof-of-concept version for people to play around with if they're interested.