Get category count relative to the current query

Nice and interesting question must say. Unfortunately, you are not going to get this to work with get_categories, so you will need another approach here.

Here is how we will do it:

• Create a very lean custom query to get all the post ID's from all posts matching the query

• Get all the categories attached to a post

• Loop through all the posts and the categories within the posts and build an array with the category names as keys and post ID's as values

• Loop through this new array, and display the category name and also count and display the amount of posts for that specific key ( category )

THE CODE:

(NOTE: The following code is untested and needs at leat PHP 5.4+ due to the new array syntax ([]))

$cats   = ( isset( $_GET['category'] ) ) ? implode( ',', array_keys( $_GET['category'] ) ) : null;$search = ( isset( $_GET['s'] ) ) ? sanitize_text_field( $_GET['s'] ) : null;$args = [    'post_type'     => 'post',    'nopaging'      => true, // Gets all posts    's'             => $search,    'category_name' => $cats,    'fields'        => 'ids', // Makes the query extremely lean, excellent for performance, only get post ID's];$q = get_posts( $args );// Define our $category_array which will hold the category name/post ID's array$category_array = [];// Define our $category_info array which will hold the category name as key and the object as value$category_info = [];foreach ( $q as $post ) {    // Get the categories attached to a post    $categories = get_the_category( $post );    foreach ( $categories as $category ) {        // Create our array which will hold the category name as key and post ID's as values        $category_array[$category->name][] = $post;        // Create an array to hold the category objects. Use names as keys and objects as values        $category_info[$category->name] = $category;    } // endforeach $categories} // endforeach $wp_query->postswp_reset_postdata();// Sort the array keys alphabetical. You can change or remove this as necessaryksort( $category_array );foreach ( $category_array as $k=>$v ) {    $category_slug = $category_info[$k]->slug;    $category_parent = $category_info[$k]->parent;    $checked = ( in_array( $category_slug, $check ) ) ? 'checked' : ''; // Just make sure that $check is defined somewhere    // Build our string    printf ( '<input id="%1$s" %4$s type="checkbox" name="category[%1$s]"><label for="%1$s" >%2$s ( %3$d )</label><br>', // I have not modified anything in this line        $category_slug, // Holds the category slug        $k, // Holds the category name        count( $v ), // Counts and return the post count        $checked    );} // endforeach $category_array