如何在PHP中正确地进行类功能内缓存

Question

What is the best practice way to do Class in-function caching in PHP. Right now I am doing:

Class Functions {
     public static function foo() {
         static $local_result;

         if(!empty($local_result) {
             return $local_result;
         }      

         $result = some_slow_http_request();
         $local_result = $result;
         return $result;
     }
}

So:

// First request makes an http request
Functions::foo();

// Second time, pull from memory, does not make an http request
Functions::foo();

Is there a better way? Are namespace collisions possible if code somewhere else changes $local_result, thinking it is a separate var?