Why not just build your own function?

function sprintf_array ($format) {
	if (1 == func_get_args () ) {
		return sprintf ($format);
	}

	$argv = func_get_args ();
	return call_user_func_array ('sprintf', $argv);
}

(Not tested, but something like this should work. :)

Yes something like this should work.

But it's not as fast as it could be.
And I personally like when thins are as fast
as possible.

I would guess that implementing it as a native PHP 
function would be at least 2x as fast.

I suppose the issue now is finding out if the core PHP 
developers consider the function to have enough value to 
add it.

My personal, non-core developer, opinion is that I don't 
like the idea of adding this function.

Perhaps instead we could overload the current 
implementations of printf and sprintf so that they can 
accept a single-dimension array as the second parameter 
(and in this case, final, parameter)?

Your solution seems fine to me.
It doesn't change the functionality I requested, so no 
objections.

Poof! Apparently Andrei is prescient. :)

Use vprintf() and vsprintf() to do exactly what you 
requested.

Not finding anything about those functions [vprintf(), 
vsprintf()] in documentation..

Already coing to be documented (according to newsgroup 
messages).
Sorry. Closing again.

It's now documented