Often you’ll create some utility functions that are called incessantly to only return the same result every time during a request. Although not a feature of Drupal itself, harnessing the power of PHP static variables can do for your code’s performance.

Drupal static variable.php

//Example #1 (simple, PHP method)

<?php
  function i_get_called_way_too_much() {
    static $static_var;
    if (!isset($static_var)) {
      // generate contents of static variable
      $static_var = 'some value';
    }
    return $static_var;
  }
?>
 
//Drupal 7 includes a new way to store and use static variables. The new method drupal_static(), providing a centralized function, allows other module to dynamically reset these variables. In a normal PHP implementation, only the function in which the variable is in scope could do this.
 
//Example #2 (Drupal 7 method)

<?php
  function i_get_called_way_too_much() {
    $var = &drupal_static(__FUNCTION__);
    if (!isset($var)) {
      // generate contents of static variable
      $var = 'some value';
    }
    return $var;
  }
  // allows for static variables to be reset from another function
  drupal_static_reset('i_get_called_way_too_much');
?>