First, let's try to add post views to the dashboard -> posts. First, we add a new column there:

add_filter('manage_posts_columns', function($columns) {
    return array_merge($columns, ['post_views' => 'Views']);
});

Then, we are going to show the number of views. We assume that (Like many other guides on the web), there is a meta key post_views holding the number of post views.

add_action('manage_posts_custom_column', function($column) {
    if ($column === 'post_views') {
        $count = get_post_meta(get_the_ID(), 'post_views_count', true);
        echo empty($count) ? 'no views :(' : "$count view :)";
    }
});

You should be able to see this new column on the posts admin table.

Finally, we have the real code to update the post_views meta every time a post is visited.

function jj_count_post_views($content)
{
    if (is_single()) {
        $postId = get_the_ID();

        update_post_meta(
            $postId,
            'post_views_count',
            (int) get_post_meta($postId, 'post_views_count', true) + 1
        );

        remove_filter('the_content', 'jj_count_post_views');
    }

    return $content;
}

add_filter('the_content', 'jj_count_post_views');

Please notice that the remove_filter is necessary, because some plugins use the_content filter to do more stuff to the content (like SEO plugins), so the_content will be called multiple times. Thanks to this answer.

P.S. Add all those codes inside theme functions.php and it works.

First, let's try to add post views to the dashboard -> posts. First, we add a new column there:

add_filter('manage_posts_columns', function($columns) {
    return array_merge($columns, ['post_views' => 'Views']);
});

Then, we are going to show the number of views. We assume that (Like many other guides on the web), there is a meta key post_views holding the number of post views.

add_action('manage_posts_custom_column', function($column) {
    if ($column === 'post_views') {
        $count = get_post_meta(get_the_ID(), 'post_views_count', true);
        echo empty($count) ? 'no views :(' : "$count view :)";
    }
});

You should be able to see this new column on the posts admin table.

Finally, we have the real code to update the post_views meta every time a post is visited.

function jj_count_post_views($content)
{
    if (is_single() && !is_preview()) {
        $postId = get_the_ID();

        update_post_meta(
            $postId,
            'post_views_count',
            (int) get_post_meta($postId, 'post_views_count', true) + 1
        );

        remove_filter('the_content', 'jj_count_post_views');
    }

    return $content;
}

add_filter('the_content', 'jj_count_post_views');

Please notice that the remove_filter is necessary, because some plugins use the_content filter to do more stuff to the content (like SEO plugins), so the_content will be called multiple times. Thanks to this answer.

Also, remove && !is_preview() if you want to count all the views, even the preview ones.

P.S. Add all those codes inside theme functions.php and it works.