No need to add the additional function, just register the new widget areas below:
register_sidebar( array (
'name' => __( 'Content Widget Area', 'startup' ),
'id' => 'content-widget-area',
'before_widget' => '<li id="%1$s" class="widget-container %2$s">',
'after_widget' => "</li>",
'before_title' => '<h3 class="widget-title">',
'after_title' => '</h3>',
) );Like so:
register_sidebar( array (
'name' => __( 'Content Widget Area', 'startup' ),
'id' => 'content-widget-area',
'before_widget' => '<li id="%1$s" class="widget-container %2$s">',
'after_widget' => "</li>",
'before_title' => '<h3 class="widget-title">',
'after_title' => '</h3>',
) );
register_sidebar( array (
'name' => __( 'Banner Center Widget Area', 'startup' ),
'id' => 'bannercenter-widget-area',
'before_widget' => '<div id="%1$s">',
'after_widget' => "</div>",
'before_title' => '<h3 class="widget-title">',
'after_title' => '</h3>',
) );
register_sidebar( array (
'name' => __( 'Banner Right Widget Area', 'startup' ),
'id' => 'bannerright-widget-area',
'before_widget' => '<div id="%1$s">',
'after_widget' => "</div>",
'before_title' => '<h3 class="widget-title">',
'after_title' => '</h3>',
) );