How to output comments number of a post per day?

Question

I have a question about the comment numbers in a post... For now, I can output the total number of a comment inside a post outside the loop. That's cool enough, but I want to get show the comment number/amount of a post PER DAY. So let's say I have a post and people are commenting 10 times today... Than, I want to show ' 10 comments' after the post title... If the day goes by and just 1 person comments the next day, I want it to output '1 comment' after the post title...

Is this possible, if yes, how?

I want to use the following function to output this "comment today per post after each post":

function wowPosts($num) {
    global $wpdb;

    $posts = $wpdb->get_results("SELECT comment_count, ID, post_title FROM $wpdb->posts ORDER BY comment_count DESC LIMIT 0 , $num");

    foreach ($posts as $post) {
        setup_postdata($post);
        $id = $post->ID;
        $title = $post->post_title;
        $count = $post->comment_count;
        $comment_count = get_comment_count($post->ID);
        $all_comments = get_comment_count( array ( 'post_id' => get_the_ID() ) );

        if ($count != 0) {
            $popular .= '<li>';
            $popular .= '<a href="' . get_permalink($id) . '" title="' . $title . '">' . $title . '</a> '. count( $all_comments ) . ' ';
            $popular .= '</li>';
        }
    }
    return $popular;
}

Answer 1

There is no argument to restrict a comment query directly to a given date. You have to filter the query later:

/**
 * Get the number of comments for a post today.
 *
 * @param  int $post_id
 * @return int
 */
function t5_count_comments_today( $post_id = NULL )
{
    if ( NULL === $post_id )
        $post_id = get_the_ID();

    add_filter( 'comments_clauses', 't5_comments_today_sql' );

    // get_comments() returns a string even with 'count' set to TRUE.
    return (int) get_comments(
        array (
            'post_id' => $post_id,
            'count'   => TRUE
        )
    );
}

/**
 * Add date specific WHERE clause to comment query.
 *
 * Deactivates itself to avoid collisions with regular comment queries.
 *
 * @wp-hook comments_clauses
 * @param   array $clauses
 * @return  array
 */
function t5_comments_today_sql( $clauses )
{
    // avoid collisions
    remove_filter( current_filter(), __FUNCTION__ );

    global $wpdb;
    $clauses['where'] .= $wpdb->prepare( ' AND comment_date >= %s', date( 'Y-m-d 00:00:00' ) );
    return $clauses;
}

Simple usage

echo t5_count_comments_today();

Or, if you don’t want to show zero comments:

$comments_today = t5_count_comments_today();
if ( 0 < $comments_today )
    echo $comments_today;

Extended use case

This adds the number to the text of comments_popup_link().

is_admin() || add_filter( 'comments_number', 't5_comment_number_today', 10, 2 );

/**
 * Add formatted number to total comments number.
 *
 * @wp-hook comments_number
 * @param   string $output
 * @param   int    $number Might be a string, so we cast it to int.
 * @return  string
 */
function t5_comment_number_today( $output, $number )
{
    // no comments at all, no need to count today's comments
    if ( 0 === (int) $number )
        return $output;

    $count = t5_count_comments_today();
    $add   = 'no comments today'; // default text

    if ( 1 === $count )
        $add = 'one comment today';

    if ( 1 < $count )
        $add = "$count comments today";

    return "$output ($add)";
}

Side note: Always use get_comments() or the class WP_Comment_Query for which get_comments() is a wrapper, because that result will be cached, so you will never have to fetch the same value for an identical argument list twice.
Avoid non-API calls with raw SQL in these cases.

Answer 2

The database table that WordPress uses to store its comments has a couple date fields in it -- comment_date and comment_date_gmt. You should be able to do something like this:

function wpse99287_comment_count( $content ) {
    global $wpdb;
    global $post;
    $today = date( 'Y-m-d 00:00:00' );
    $tomorrow = date( 'Y-m-d 23:59:59' );
    $sql = "SELECT COUNT(comment_id)
            FROM {$wpdb->comments} 
            WHERE comment_post_ID = {$post->ID}
            AND comment_approved = 1
            AND comment_date >= '$today'
            AND comment_date <= '$tomorrow'";
    $comment_count = $wpdb->get_var( $sql );
    $content = "<div class='comment-count'>$comment_count comment(s) today</div>" . $content;
}
add_filter( 'the_content', 'wpse99287_comment_count' );

That will add the comment count in a <div> at the start of your post's content.

References

wpdb class