WordPress at a glance
filter is not described

content_pagination filter-hook . WP 4.4.0

Filters the "pages" derived from splitting the post content.

"Pages" are determined by splitting the post content based on the presence of <!-- nextpage --> tags.

Usage

add_filter( 'content_pagination', 'filter_function_name_1940', 10, 2 );
function filter_function_name_1940( $pages, $post ){
	// filter...

	return $pages;
}
$pages(array)
Array of "pages" derived from the post content. of <!-- nextpage --> tags..
$post(WP_Post)
Current post object.

Where the hook is called

WP_Query::setup_postdata()
wp-includes/class-wp-query.php 4028
$pages = apply_filters( 'content_pagination', $pages, $post );

Where the hook is used (in WP core)

Does not used.