Drupal许多的函数中都使用了静态变量。按照通常的用法，静态变量的使用应该是这样的：
function drupal_set_title($title = NULL) {
static $stored_title;
if (isset($title)) {
$stored_title = $title;
}
return $stored_title;
}但是Drupal使用的方式有些不同。主要的考量应该是这样：可能会有几十上百个函数中使用了静态变量，Drupal需要在某一时刻对这些静态变量都做reset处理。这个时候，不可能对这几十上百个函数都重新调用一次。因此，Drupal需要一种机制，来集中地存放静态变量，这就是函数druap_static()存在的目的：
function &drupal_static($name, $default_value = NULL, $reset = FALSE) {
static $data = array(), $default = array();
// First check if dealing with a previously defined static variable.
if (isset($data[$name]) || array_key_exists($name, $data)) {
// Non-NULL $name and both $data[$name] and $default[$name] statics exist.
if ($reset) {
// Reset pre-existing static variable to its default value.
$data[$name] = $default[$name];
}
return $data[$name];
}
// Neither $data[$name] nor $default[$name] static variables exist.
if (isset($name)) {
if ($reset) {
// Reset was called before a default is set and yet a variable must be
// returned.
return $data;
}
// First call with new non-NULL $name. Initialize a new static variable.
$default[$name] = $data[$name] = $default_value;
return $data[$name];
}
// Reset all: ($name == NULL). This needs to be done one at a time so that
// references returned by earlier invocations of drupal_static() also get
// reset.
foreach ($default as $name => $value) {
$data[$name] = $value;
}
// As the function returns a reference, the return should always be a
// variable.
return $data;
}注意，这里drupal_static()返回的是引用。
使用drupal_static()后的函数drupal_set_title()是这样的：
function drupal_set_title($title = NULL, $output = CHECK_PLAIN) {
$stored_title = &drupal_static(__FUNCTION__);
if (isset($title)) {
$stored_title = $title;
}
return $stored_title;
}当需要reset集中存储的静态变量时，可以调用函数drupal_static_reset()：
function drupal_static_reset($name = NULL) {
drupal_static($name, NULL, TRUE);
}