Wordpress - Adding iframe Content to Sidebar Widget

Just create a widget that doesn’t filter your input. This is probably the most simple widget with user input you can build.

Here is the widget I use in my plugin Magic Widgets.

/**
 * Simplified variant of the native text widget class.
 *
 * @author Fuxia Scholz
 * @version 1.0
 */
class Unfiltered_Text_Widget extends WP_Widget
{
    /**
     * @uses apply_filters( 'magic_widgets_name' )
     */
    public function __construct()
    {
        // You may change the name per filter.
        // Use add_filter( 'magic_widgets_name', 'your custom_filter', 10, 1 );
        $widgetname = apply_filters( 'magic_widgets_name', 'Unfiltered Text' );
        parent::__construct(
            'unfiltered_text'
        ,   $widgetname
        ,   array( 'description' => 'Pure Markup' )
        ,   array( 'width' => 300, 'height' => 150 )
        );
    }

    /**
     * Output.
     *
     * @param  array $args
     * @param  array $instance
     * @return void
     */
    public function widget( $args, $instance )
    {
        echo $instance['text'];
    }

    /**
     * Prepares the content. Not.
     *
     * @param  array $new_instance New content
     * @param  array $old_instance Old content
     * @return array New content
     */
    public function update( $new_instance, $old_instance )
    {
        return $new_instance;
    }

    /**
     * Backend form.
     *
     * @param array $instance
     * @return void
     */
    public function form( $instance )
    {
        $instance = wp_parse_args( (array) $instance, array( 'text' => '' ) );
        $text     = format_to_edit($instance['text']);
?>
        <textarea class="widefat" rows="7" cols="20" id="<?php
            echo $this->get_field_id( 'text' );
        ?>" name="<?php
            echo $this->get_field_name( 'text' );
        ?>"><?php
            echo $text;
        ?></textarea>
        <?php
        /* To enable the preview uncomment the following lines.
         * Be aware: Invalid HTML may break the rest of the site and it
         * may disable the option to repair the input text.

        ! empty ( $text )
            and print '<h3>Preview</h3><div style="border:3px solid #369;padding:10px">'
                . $instance['text'] . '</div>';
        /**/
        ?>
<?php
    }
}

You register the widget with:

add_action( 'widgets_init', 'register_unfiltered_text_widget', 20 );

function register_unfiltered_text_widget()
{
    register_widget( 'Unfiltered_Text_Widget' );
}

Now you get a new widget in wp-admin/widgets.php:

I put just two cool Youtube videos as iframes and a <hr> into the widget.
Output: