It looks like the override_function() has a bug that prevents from using it to override two or more functions, since it issues this error:

Fatal error: Cannot redeclare __overridden__()

Judging by the C code for PHP’s override_function() function, instead of hardcoding the overriden function name it was planed to generate random names, but for reasons unknown to me this never happened.

Anyway, I can’t believe the fix for this is so simple and yet the solution didn’t appear in PHP’s excellent online documentation. It had me lost for a while, but it’s as simple as renaming the overriden function!! This is from the wrapper I mentioned, that will be distributed with Cherokee shortly:

foreach ($substs as $func => $ren_func) {
    override_function($func, $args[$func], "return $substs[$func];");
    rename_function("__overridden__", $ren_func);
}