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The Dashboard Widgets API (added in WP 2.7) makes it very simple to add new widgets to the administration dashboard. Doing so requires working knowledge of PHP and the WordPress Plugin API, but to plugin or theme authors familiar with hooking actions and filters it only takes a few minutes and can be a great way to make your plugin even more useful.
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The main tool needed to add Dashboard Widgets is the wp_add_dashboard_widget() function:
wp_add_dashboard_widget($widget_id, $widget_name, $callback, $control_callback = null)
To run the function you will need to hook into the correct action, in this case, 'wp_dashboard_setup'. Here's how it looks in the core code:
do_action( 'wp_dashboard_setup' );
Here's the most bare outline of a widget I could come up with.
// Create the function to output the contents of our Dashboard Widget
function example_dashboard_widget_function() {
// Display whatever it is you want to show
echo "Hello World, I'm a great Dashboard Widget";
}
// Create the function use in the action hook
function example_add_dashboard_widgets() {
wp_add_dashboard_widget('example_dashboard_widget', 'Example Dashboard Widget', 'example_dashboard_widget_function');
}
// Hook into the 'wp_dashboard_setup' action to register our other functions
add_action('wp_dashboard_setup', 'example_add_dashboard_widgets' );
Normally you should just let the users of your plugin put your Dashboard Widget wherever they want by dragging it around. There currently isn't an easy API way to pre-sort the default widgets, meaning your new widget will always be at the bottom of the list. Until sorting is added to the API its a bit complicated to get around this problem.
Below is an example hooking function that will try to put your widget before the default ones. It does so by manually altering the internal array of metaboxes (of which dashboard widgets are one type) and putting your widget at the top of the list so it shows first.
function example_add_dashboard_widgets() {
wp_add_dashboard_widget('example_dashboard_widget', 'Example Dashboard Widget', 'example_dashboard_widget_function');
// Globalize the metaboxes array, this holds all the widgets for wp-admin
global $wp_meta_boxes;
// Get the regular dashboard widgets array
// (which has our new widget already but at the end)
$normal_dashboard = $wp_meta_boxes['dashboard']['normal']['core'];
// Backup and delete our new dashbaord widget from the end of the array
$example_widget_backup = array('example_dashboard_widget' => $normal_dashboard['example_dashboard_widget']);
unset($normal_dashboard['example_dashboard_widget']);
// Merge the two arrays together so our widget is at the beginning
$sorted_dashboard = array_merge($example_widget_backup, $normal_dashboard);
// Save the sorted array back into the original metaboxes
$wp_meta_boxes['dashboard']['normal']['core'] = $sorted_dashboard;
}
Unfortunately this only works for people who have never re-ordered their widgets. Once a user has done so their existing preferences will override this and they will have to move your widget to the top for it to stay there.
In some situations, especially on multi-user blogs, it may be useful to completely remove widgets from the interface. Each individual user can, by default, turn off any given widget using the "Screen Options" tab at the top, but if you have a lot of non-technical users it might be nicer for them to not see it at all.
To remove dashboard widget, use the remove_meta_box() function. See the example code below for the required parameters.
These are the names of the default widgets on the dashboard:
Main column:
$wp_meta_boxes['dashboard']['normal']['high']['dashboard_browser_nag'] $wp_meta_boxes['dashboard']['normal']['core']['dashboard_right_now'] $wp_meta_boxes['dashboard']['normal']['core']['dashboard_recent_comments'] $wp_meta_boxes['dashboard']['normal']['core']['dashboard_incoming_links'] $wp_meta_boxes['dashboard']['normal']['core']['dashboard_plugins']
Side Column:
$wp_meta_boxes['dashboard']['side']['core']['dashboard_quick_press'] $wp_meta_boxes['dashboard']['side']['core']['dashboard_recent_drafts'] $wp_meta_boxes['dashboard']['side']['core']['dashboard_primary'] $wp_meta_boxes['dashboard']['side']['core']['dashboard_secondary']
Here is an example function that removes the QuickPress and Incoming Links widgets.
// Create the function to use in the action hook
function example_remove_dashboard_widgets() {
remove_meta_box( 'dashboard_quick_press', 'dashboard', 'side' );
remove_meta_box( 'dashboard_incoming_links', 'dashboard', 'normal' );
}
// Hoook into the 'wp_dashboard_setup' action to register our function
add_action('wp_dashboard_setup', 'example_remove_dashboard_widgets' );
The function doesn't allow you to choose where you want your widget to go and will automatically add it to the "core" which is the left side. However you are able to get it on the right side very easily. After creating the widget what you do is.
// Global the $wp_meta_boxes variable (this will allow us to alter the array)
global $wp_meta_boxes;
// Then we make a backup of your widget
$my_widget = $wp_meta_boxes['dashboard']['normal']['core']['{widget id here}'];
// We then unset that part of the array
unset($wp_meta_boxes['dashboard']['normal']['core']['{widget id here}']);
// Now we just add your widget back in
$wp_meta_boxes['dashboard']['side']['core']['{widget id here}'] = $my_widget;
If you need to aggregate RSS in your widget you should take a look at the way the existing plugins are set up with caching in /wp-admin/includes/dashboard.php.