pager_query_add_page(array $query, $element, $index)
Gets the URL query parameter array of a pager link.
Adds to or adjusts the 'page' URL query parameter so that if you follow the link, you'll get page $index for pager $element on the page.
The 'page' URL query parameter is a comma-delimited string, where each value is the target content page for the corresponding pager $element. For instance, if we have 5 pagers on a single page, and we want to have a link to a page that should display the 6t