Adding a Fourth Footer Widget

HI,

I have placed the following into functions.php in my child theme, but it seems to not be working. Any troubleshooting tips please?

<?php
/**
* This is where you can copy and paste your functions !
*/

// Adds a widget area. It gets registered automatically as part of the arra
add_filter( 'tc_footer_widgets', 'my_footer_widgets');
function my_footer_widgets( $default_widgets_area ) {
    $default_widgets_area['footer_four'] = array(
          'name'                 => __( 'Footer Widget Area Four' , 'customizr' ),
          'description'          => __( 'Just use it as you want !' , 'customizr' )
    );
    return $default_widgets_area;
}

// Style all the footer widgets so they take up the right space
add_filter( 'footer_one_widget_class', 'my_footer_widget_class');
add_filter( 'footer_two_widget_class', 'my_footer_widget_class');
add_filter( 'footer_three_widget_class', 'my_footer_widget_class');
add_filter( 'footer_four_widget_class', 'my_footer_widget_class');
function my_footer_widget_class() {
    return 'span3';
}