Add class to before_widget from within a custom widget

The question:

I have a simple custom widget that asks for its width (that is used later in the front end). The width field is a select dropdown, so a user have predefined options.

I will have many instances of my widget, each will have its own width setup.

Now, in my widget code I have the following code:

echo $before_widget;

which results in:

<div class="widget my" id="my-widget-1"></div>

What I’d like to do is somehow hook into $before_widget and add my own class (the specified width from the select dropdown). So, I want the following markup:

<div class="widget my col480" id="my-widget-3"></div>

And if there is no class specified then I want to add class="col480".

How do I achieve this?

Thanks for help!

The Solutions:

Below are the methods you can try. The first solution is probably the best. Try others if the first one doesn’t work. Senior developers aren’t just copying/pasting – they read the methods carefully & apply them wisely to each case.

Method 1

Aha, so the $before_widget variable is a string representing div element: <div class="widget my" id="my-widget-1"> . So I checked the $before_widget for the “class” sub-string and added my $widget_width value to it.

The code is from my custom widget file:

function widget( $args, $instance ) {
  extract( $args );
  ... //other code

  $widget_width = !empty($instance['widget_width']) ? $instance['widget_width'] : "col300";
  /* Add the width from $widget_width to the class from the $before widget */
  // no 'class' attribute - add one with the value of width
  if( strpos($before_widget, 'class') === false ) {
    // include closing tag in replace string
    $before_widget = str_replace('>', 'class="'. $widget_width . '">', $before_widget);
  // there is 'class' attribute - append width value to it
  else {
    $before_widget = str_replace('class="', 'class="'. $widget_width . ' ', $before_widget);
  /* Before widget */
  echo $before_widget;

  ... //other code

I wanted to add my $widget_width variable to the widget div element within my own widget code (while I had an easy access to the $widget_width variable).

Hope that makes sense and will help someone.

Thanks, Dasha

Method 2

you can use dynamic_sidebar_params filter hook to find your widget and add your classes to it:

add_filter('dynamic_sidebar_params', 'add_classes_to__widget'); 
function add_classes_to__widget($params){
    if ($params[0]['widget_id'] == "my-widget-1"){ //make sure its your widget id here
        // its your widget so you add  your classes
        $classe_to_add = 'col480 whatever bla bla '; // make sure you leave a space at the end
        $classe_to_add = 'class=" '.$classe_to_add;
        $params[0]['before_widget'] = str_replace('class="',$classe_to_add,$params[0]['before_widget']);
    return $params;

Method 3

Another way I found to add a class for a custom widget is to use the the ‘classname‘ key of your construct function like in:

class My_Widget_Class extends WP_Widget {
// Prior PHP5 use the children class name for the constructor…
// function My_Widget_Class()
       function __construct() {
            $widget_ops = array(
                'classname' => 'my-class-name',
                'description' => __("Widget for the sake of Mankind",'themedomain'),
            $control_ops = array(
                'id_base' => 'my-widget-class-widget'
   //some more code after...

   // Call parent constructor you may substitute the 1st argument by $control_ops['id_base'] and remove the 4th.

And be sure to use default ‘before_widget‘ in your theme or if you use register_sidebar() in function.php, do it like this:

//This is just an example.
          'name'=> 'Sidebar',
            'id' => 'sidebar-default',
            'class' => '',//I never found where this is used...
            'description' => 'A sidebar for Mankind',
            'before_widget' => '<aside id="%1$s" class="widget %2$s">',//This is the important code!!
            'after_widget' => '</aside>',
            'before_title' => '<h3>',
            'after_title' => '</h3>',

Then on every instances of your widget, you will have the class ‘widget my-class-name’ like this:

<aside class="widget my-class-name" id="my-widget-class-widget-N"><!-- where N is a number -->
  <h3>WIDGET TITLE</h3>

You may also call the parent constructor first and then append whatever class name you want :

class My_Widget_Class extends WP_Widget {
    // Better defining the parent argument list …
    function __construct($id_base, $name, $widget_options = array(), $control_options = array())
    {    parent::__construct($id_base, $name, $widget_options, $control_options);
         // Change the class name after
         $this->widget_options['classname'].= ' some-extra';

Method 4

first add a custom placeholder class in the constructor

public function __construct() {
   $widget_ops  = array(
      'classname'                   =>; 'widget_text eaa __eaa__', //__eaa__ is my placeholder css class
      'description'                 =>; __( 'AdSense ads, arbitrary text, HTML or JS.','eaa' ),
      'customize_selective_refresh' =>; true,
   $control_ops = array( 'width' =>; 400, 'height' =>; 350 );
   parent::__construct( 'eaa', __( 'Easy AdSense Ads &amp; Scripts', 'eaa' ), $widget_ops, $control_ops );

Then replace it with the class/es of your choice based on the widget options like this

if ( $instance['no_padding'] ) {
   $args['before_widget'] = str_replace( '__eaa__', 'eaa-clean', $args['before_widget'] );

You can find the details with example at

Method 5

You can try this filter:

 * This function loops through all widgets in sidebar 
 * and adds a admin form value to the widget as a class name  
 * @param array $params Array of widgets in sidebar
 * @return array

add_filter( 'dynamic_sidebar_params', 'nen_lib_add_class_to_widget' );
function nen_lib_add_class_to_widget( $params )
    foreach( $params as $key => $widget )
        if( !isset($widget['widget_id']) ) continue;

        // my custom function to get widget data from admin form (object)
        $widget_data = nen_get_widget_data($widget['widget_id']) ;

        // check if field excists and has value
        if( isset($widget_data->wm_name) && $widget_data->wm_name )
            // convert and put value in array
            $classes = array( sanitize_title( $widget_data->wm_name ) );

            // add filter, to be able to add more
            $classes = apply_filters( 'nen_lib_add_class_to_widget' , $classes , $widget['widget_id'] , $widget , $widget_data  );

            // get 'before_widget' element, set find and replace
            $string     = $params[$key]['before_widget'];
            $find       = '"widget ';
            $replace    = '"widget '.implode( ' ' , $classes ).' ';

            // new value
            $new_before = str_replace( $find , $replace , $string ) ;

            // set new value
            $params[$key]['before_widget'] = $new_before;
    return $params;

All methods was sourced from or, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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