Whether widget is displayed on the front-end.

Either $callback or $id_base can be used $id_base is the first argument when extending WP_Widget class Without the optional $widget_id parameter, returns the ID of the first sidebar in which the first instance of the widget with the given callback or $id_base is found. With the $widget_id parameter, returns the ID of the sidebar where the widget with that callback/$id_base AND that ID is found.

NOTE: $widget_id and $id_base are the same for single widgets. To be effective this function has to run after widgets have initialized, at action ‘init’ or later.

Signature

is_active_widget( $callback = false, $widget_id = false, $id_base = false, $skip_inactive = true )
callback
 (string) Optional, Widget callback to check.
Default: false
widget_id
 (int) Optional, but needed for checking. Widget ID.
Default: false
id_base
 (string) Optional, the base ID of a widget created by extending WP_Widget.
Default: false
skip_inactive
 (boolean) Optional, whether to check in 'wp_inactive_widgets'.
Default: true

Return

(mixed) false if widget is not active or id of sidebar in which the widget is active.

Source

function is_active_widget($callback = false, $widget_id = false, $id_base = false, $skip_inactive = true) {
	global $wp_registered_widgets;

	$sidebars_widgets = wp_get_sidebars_widgets();

	if ( is_array($sidebars_widgets) ) {
		foreach ( $sidebars_widgets as $sidebar => $widgets ) {
			if ( $skip_inactive && ( 'wp_inactive_widgets' === $sidebar || 'orphaned_widgets' === substr( $sidebar, 0, 16 ) ) ) {
				continue;
			}

			if ( is_array($widgets) ) {
				foreach ( $widgets as $widget ) {
					if ( ( $callback && isset($wp_registered_widgets[$widget]['callback']) && $wp_registered_widgets[$widget]['callback'] == $callback ) || ( $id_base && _get_widget_id_base($widget) == $id_base ) ) {
						if ( !$widget_id || $widget_id == $wp_registered_widgets[$widget]['id'] )
							return $sidebar;
					}
				}
			}
		}
	}
	return false;
}
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