get_categories order by last post - wordpress

Question

What is the best and shortest way in Wordpress to get_categories ordered by last posted article?
Means that categories with recent posts should appear first, is it available somehow?

Answer 1

Try it:
function get_sorted_categories( $order_by = 'id', $args = array() ){
global $wpdb;
$category = get_categories( $args );
$order = [
'id' => 'post.ID',
'date' => 'post.post_date',
'modified' => 'post.post_modified',
];
$order_by = $order[ $order_by ];
$q = $wpdb->get_results("SELECT tax.term_id FROM `{$wpdb->prefix}term_taxonomy` tax
INNER JOIN `{$wpdb->prefix}term_relationships` rel ON rel.term_taxonomy_id = tax.term_id
INNER JOIN `{$wpdb->prefix}posts` post ON rel.object_id = post.ID WHERE tax.taxonomy = 'category' AND post.post_type = 'post' AND post.post_status = 'publish' ORDER BY {$order_by} DESC");
$sort = array_flip( array_unique( wp_list_pluck( $q, 'term_id' ) ) );
usort( $category, function( $a, $b ) use ( $sort, $category ) {
if( isset( $sort[ $a->term_id ], $sort[ $b->term_id ] ) && $sort[ $a->term_id ] != $sort[ $b->term_id ] )
$res = ($sort[ $a->term_id ] > $sort[ $b->term_id ]) ? 1 : -1;
else if( !isset( $sort[ $a->term_id ] ) && isset( $sort[ $b->term_id ] ) )
$res = 1;
else if( isset( $sort[ $a->term_id ] ) && !isset( $sort[ $b->term_id ] ) )
$res = -1;
else
$res = 0;
return $res;
} );
return $category;
}
print_r( get_sorted_categories() );
print_r( get_sorted_categories('date') );
print_r( get_sorted_categories('modified') );
Get categories order by (post ID | post date | post modified date). Without any loop and fast!

Answer 2

I think the easiest way would be to loop through all of your posts ordered by post_date and then save the categories to an array. You can then loop through the categories and display them. They will be in order.
Something like this:
<?php
// Initiate array
$cats = array();
// Query arguments
$args = array(
'post_type' => 'post',
'posts_per_page' => -1,
'orderby' = 'post_date'.
'order' => 'DESC'
);
// The query
$query = new WP_Query($args);
// The loop
if($query->have_posts()) {
while($query->have_posts()) {
$query->the_post();
// Get the term object
$term = get_the_category();
// Make sure the term doesn't already exist in the array
if(!array_key_exists($term[0]->ID, $cats)) {
// Add the terms to the array
$cats[$term[0]->ID] = $term;
}
}
}
foreach($cats as $cid => $cat) {
// Loop through the categories here
}
?>
Of course, as mentioned in the comment above you could also do it the other way around and loop through the categories first then sort the array. Something like this could do:
<?php
// Initiate array
$cats = get_categories();
$recent_cats = array();
foreach($cats as $k => $cat) {
// Query arguments
$args = array(
'post_type' => 'post',
'posts_per_page' => 1,
'orderby' = 'post_date'.
'order' => 'DESC',
'cat' => $cat->term_id
);
// The query
$query = new WP_Query($args);
// The loop
if($query->have_posts()) {
while($query->have_posts()) {
$query->the_post();
$date_str = strtotime(the_date());
if(!array_key_exists($date_str, $recent_cats)) {
$recent_cats[$date_str] = $cat->name;
}
}
}
}
krsort($recent_cats);
// Loop through $recent_cats here
?>