您可以使用WP_Query 像这样：

// we get the date for today
$today = getdate();
//we set the variables, i am ignoring sticky posts so they dont get counted
$args = array(
    \'ignore_sticky_posts\' => 1,
    \'posts_per_page\' => -1, //all posts 
    \'date_query\' => array(
        array(
            \'year\'  => $today["year"],
            \'month\' => $today["mon"],
            \'day\'   => $today["mday"],
        ),
    ),
);

//we create the query
$today_posts = new WP_Query( $args );
//the result already has a property with the number of posts returned
$count = $today_posts->post_count;
//show it
echo $count;