//递归返回字符串键名全为小写或大写的数组
function recurse_array_change_key_case(&$input, $case = CASE_LOWER){
    if(!is_array($input))
        return;

    foreach($input as $key => $val)
    {
        //1
        if($case == CASE_UPPER)
        {
            $newkey = strtoupper($key);
        }
        //0
        elseif($case == CASE_LOWER)
        {
            $newkey = strtolower($key);
        }
        
        if($newkey != $key)
        {
            unset($input[$key]);
            $input[$newkey] = $val;
        }
        if(is_array($val))
        {
            //###注：此处的参数须为$input[$newkey]，而不是$val,如果是$val,需要在foreach中 $key=>&$val
            recurse_array_change_key_case($input[$newkey], $case);
        }
    }
}