+ * Set the uninstallation hook for a plugin.
+ *
+ * Registers the uninstall hook that will be called when the user clicks on the
+ * uninstall link that calls for the plugin to uninstall itself. The link won't
+ * be active unless the plugin hooks into the action.
+ *
+ * The plugin should not run arbitrary code outside of functions, when
+ * registering the uninstall hook. In order to run using the hook, the plugin
+ * will have to be included, which means that any code laying outside of a
+ * function will be run during the uninstall process. The plugin should not
+ * hinder the uninstall process.
+ *
+ * If the plugin can not be written without running code within the plugin, then
+ * the plugin should create a file named 'uninstall.php' in the base plugin
+ * folder. This file will be called, if it exists, during the uninstall process
+ * bypassing the uninstall hook. The plugin, when using the 'uninstall.php'
+ * should always check for the 'WP_UNINSTALL_PLUGIN' constant, before
+ * executing.
+ *
+ * @since 2.7
+ *
+ * @param string $file
+ * @param callback $callback The callback to run when the hook is called.
+ */
+function register_uninstall_hook($file, $callback) {
+ // The option should not be autoloaded, because it is not needed in most
+ // cases. Emphasis should be put on using the 'uninstall.php' way of
+ // uninstalling the plugin.
+ $uninstallable_plugins = (array) get_option('uninstall_plugins');
+ $uninstallable_plugins[plugin_basename($file)] = $callback;
+ update_option('uninstall_plugins', $uninstallable_plugins);
+}
+
+/**
+ * Calls the 'all' hook, which will process the functions hooked into it.