public function getCompiledConfig()
    {
        if ($this->compiled_config === null) {
            // see if template needs compiling.
            if ($this->mustCompile()) {
                $this->compileConfigSource();
            } else {
                $this->compiled_config = file_get_contents($this->getCompiledFilepath());
            }
        }

        return $this->compiled_config;
    }