What is the best way to create a variable that is accessed by the different views of my module (block, page etc), but that is destroyed at every new page request?
I've been using variable_set to store information that is used throughout my module, but this seems to persist across page requests. Is there a hook I can implement to call variable_del for every outgoing page, or is there a better way of storing variables in my module that do not persist across page loads?
The variable_set() and variable_get() functions are made to set/get a persistent variable. So they should not be used to persist data within a single page request. The drupal_static() function is made for this task and is well documented. Off course, you could also go with a static variable without bothering about drupal_static(). But drupal_static() will make your code more maintainable and future proof.
/**
* Set or get the shared foo variable.
*
* @param $new_value
* (optional) If set, the new value to assign to the foo variable.
*
* @return
* The value of the foo variable. If $new_value is set this would be
* the previous value.
*/
function MODULE_foo($new_value = NULL) {
$value = drupal_static(__FUNCTION__, NULL);
$previous_value = $value;
if ($new_value !== NULL) {
$value = $new_value;
}
return $previous_value;
}
Not only does variable_set persist across pages, it nukes the cache every time it is called. It should only really be used for settings, and similar read-mostly uses.
If you read my answer to Where do I declare a global variable?, I outline a few methods that should work. I typically use the method,
function foo_get_the_service ()
{
static $service;
if (! isset($service)) {
$service = foo_init_the_service();
}
return $service;
}
which works well for me when I really do need a global.
