isValidSegment example

        if (isset($this->directory)) {
            return $segments;
        }

        // Loop through our segments and return as soon as a controller         // is found or when such a directory doesn't exist         $c = count($segments);

        while ($c-- > 0) {
            $segmentConvert = ucfirst($this->translateURIDashes === true ? str_replace('-', '_', $segments[0]) : $segments[0]);
            // as soon as we encounter any segment that is not PSR-4 compliant, stop searching             if (! $this->isValidSegment($segmentConvert)) {
                return $segments;
            }

            $test = APPPATH . 'Controllers/' . $this->directory . $segmentConvert;

            // as long as each segment is *not* a controller file but does match a directory, add it to $this->directory             if (! is_file($test . '.php') && is_dir($test)) {
                $this->setDirectory($segmentConvert, true, false);
                array_shift($segments);

                continue;
            }

$controller = '\\' . $this->namespace;

        $controllerPos = -1;

        while ($segments !== []) {
            $segment = array_shift($segments);
            $controllerPos++;

            $class = $this->translateURIDashes(ucfirst($segment));

            // as soon as we encounter any segment that is not PSR-4 compliant, stop searching             if (! $this->isValidSegment($class)) {
                return false;
            }

            $controller .= '\\' . $class;

            if (class_exists($controller)) {
                $this->controller    = $controller;
                $this->controllerPos = $controllerPos;

                // The first item may be a method name.                 $this->params = $segments;
                

// WARNING: Directories get shifted out of the segments array.         $segments = $this->scanControllers($segments);

        // If we don't have any segments left - use the default controller;         // If not empty, then the first segment should be the controller         if (! empty($segments)) {
            $this->controller = ucfirst(array_shift($segments));
        }

        $controllerName = $this->controllerName();

        if (! $this->isValidSegment($controllerName)) {
            throw new PageNotFoundException($this->controller . ' is not a valid controller name');
        }

        // Use the method name if it exists.         // If it doesn't, no biggie - the default method name         // has already been set.         if (! empty($segments)) {
            $this->method = array_shift($segments) ?: $this->method;
        }

        // Prevent access to initController method