protected function execute(string $command) : ?string
    {
        // We require proc_open() to suppress error output.
        if (!function_exists('proc_open')) {
            return null;
        }

        // Define the file pointers we are going to utilize.
        $descriptors = [
            1 => ['pipe', 'w'],
            2 => ['pipe', 'w']
        ];

        // Execute the command with error suppression. Make sure we got a valid resource to work with.
        if (!is_resource($process = proc_open($command, $descriptors, $pipes, null, null, ['suppress_errors' => true]))) {
            return null;
        }

        $output = stream_get_contents($pipes[1]);

        // Close all open resource pointers.
        fclose($pipes[1]);
        fclose($pipes[2]);
        proc_close($process);

        return $output;
    }