Adding the NextPage Button Back to the Toolbar

There’s a convenient button for the <!--more--> tag on the toolbar, but nothing for the <!--nextpage--> quicktag. Fix that with this

add_filter('mce_buttons','add_nextpage_button');
function add_nextpage_button($buttons) {
    //array_splice so we can insert the new item without overwriting an existing button
    array_splice($buttons, 15,0, 'wp_page' );
    return $buttons;
}