Display Post Views

<?php
function track_post_views($post_id) {
    if (!is_single()) return;
    if (empty($post_id)) {
        global $post;
        $post_id = $post->ID;
    }
    $views = get_post_meta($post_id, 'post_views', true);
    if ($views == '') {
        $views = 0;
        delete_post_meta($post_id, 'post_views');
        add_post_meta($post_id, 'post_views', '0');
    } else {
        $views++;
        update_post_meta($post_id, 'post_views', $views);
    }
}
add_action('wp_head', 'track_post_views');

function display_post_views() {
    global $post;
    $views = get_post_meta($post->ID, 'post_views', true);
    echo '<p>Views: ' . esc_html($views) . '</p>';
}
add_action('the_content', 'display_post_views');
?>