Using drupal_static() on your helper functions is a great habit to get into when developing your modules. Drupal static ensures that your function will only run through its logic once during the bootstrap process. Depending on your functions logic, this can start saving lots of processing time if your function is being called multiple times during bootstrap or page load.

Implementing drupal_static

Let's take the following function for example. Here is helper function takes a url string from the ELMSLN network and breaks it up into identifiable parts.