Provides a "view all" (single page) option for content paged using WordPress' <!--nextpage--> Quicktag (multipage posts).
add_query_arg()as identified by Sucuri: https://blog.sucuri.net/2015/04/security-advisory-xss-vulnerability-affecting-multiple-wordpress-plugins.html.
init, both to ensure external code can interact with filters and to avoid PHP notices.
$multipagevariable will function properly. Props @batmoo.
the_contentfilter, global variables are overridden in the
the_postaction. Ensures that infinite loops don't result from shortcode processing and other uses of the
the_contentfilter. Props to the WordPress.com VIP Support team (batmoo) and stevenkword.
vapp_display_linkfilter to allow plugins and themes to suppress the automatic View All link on specific posts. Return
falseto suppress the link. Filter also passes post ID, plugin options, and post object.