Share a value between two different hooks

Question

I have 2 hook functions in my module: hook_views_pre_render() and hook_form_alter(); in hook_views_pre_render(), I retrieve some data about what nodes that are available that I need in hook_form_alter().

I'm looking for a way to pass the data from hook_views_pre_render() to hook_form_alter(). It seems simple, but I can't get it to work. Does anyone any idea?

What works for the moment is to add global $aVariable to both the hook functions, but I believe there should be a better way.

Answer 1

you can use variable_set($name, $value) and variable_get($name, $default = NULL)

Answer 2

In Drupal 7, drupal_static() could be used too, if the stored value doesn't need to be persistent between different pages.

drupal_static() is normally called as drupal_static(__FUNCTION__, $default_value), but if you use the name of the function, you can access the same value accessed from the function that calls drupal_static().

Using variable_set() and variable_get() the value is persistent between different pages, and it is not automatically removed. If the first hook execute code similar to the following one, then the second module would get an older value.

if ($condition) {
  variable_set($variable_name, $value);
}

Rather than using such code, the first hook should execute code similar to the following one.

if ($condition) {
  variable_set($variable_name, $value);
}
else {
  variable_del($variable_name);
}

Whatever method you choose, be sure the hook reading the value is effectively running after the hook setting that value.

Answer 3

If you need to pass information that is only available in hook_views_pre_render to hook_form_alter a global variable might be your best option; preferably named to make it's restricted role clear, e.g., _mymodule_available_nodes.

The best approach would be to add your data to any objects the two calls have in common. In this case unfortunately there there appear to be none in common, so this won't work.

You might be able to use session data, but that would be overkill for this application, and doesn't seem to offer clear benefits over a global.

I don't recommend using variable_set/variable_get. variable_set clears the variable cache on every call, plus all variable values are fetched on every page request. This is not a good match for data that is constantly changing, and of potentially large size.