cache minimal

<?php

/**
 * Class and Function List:
 * Function list:
 * - enable_dynamic_caching()
 * - html_cache()
 * - get_html_cache()
 * - add_cache_stats_in_admin_menu()
 * - cache_stats_page()
 * - clean_cache()
 * - add_cache_stats_in_admin_bar()
 * - clean_cache_on_browser_hard_refresh()
 * - clean_cache_after_7_days()
 */
// Enable dynamic caching
add_action('init', 'enable_dynamic_caching');

function enable_dynamic_caching()
{
    // Create HTML cache of pages in WordPress
    if (!is_admin())
    {
        ob_start('html_cache');
    }
}

// Serve the HTML pages to visitors
function html_cache($buffer)
{
    // Do not cache WooCommerce pages
    if (function_exists('is_woocommerce') && is_woocommerce())
    {
        return $buffer;
    }
    // Add a comment in footer source code with page load time
    $buffer .= '<!-- Page generated in ' . timer_stop(0) . ' seconds. Last edited: ' . get_the_modified_date() . '. Page size: ' . size_format(strlen($buffer)) . '. Expiration date: ' . date('Y-m-d H:i:s', time() + 604800) . ' -->' . "\n";
    // Update the HTML pages on changes in content
    if (is_singular())
    {
        $buffer = get_html_cache($buffer);
    }
    return $buffer;
}

// Get HTML cache
function get_html_cache($buffer)
{
    $url = $_SERVER['REQUEST_URI'];
    $html_cache_file = md5($url) . '.html';
    $html_cache_path = WP_CONTENT_DIR . '/cache/' . $html_cache_file;
    global $wp_filesystem;
    if (!$wp_filesystem)
    {
        require_once (ABSPATH . '/wp-admin/includes/file.php');
        WP_Filesystem();
    }
    if ($wp_filesystem->exists($html_cache_path))
    {
        $buffer = file_get_contents($html_cache_path);
    }
    else
    {
        file_put_contents($html_cache_path, $buffer);
    }
    return $buffer;
}

// Add cache stats in Cache menu in Wordpress admin
add_action('admin_menu', 'add_cache_stats_in_admin_menu');

function add_cache_stats_in_admin_menu()
{
    add_submenu_page('options-general.php', 'Cache Stats', 'Cache Stats', 'manage_options', 'cache-stats', 'cache_stats_page');
}

function cache_stats_page()
{
    $cache_path = WP_CONTENT_DIR . '/cache/';
    $cache_files = glob($cache_path . '*.html');
    $cache_count = count($cache_files);
    $cache_size = 0;
    foreach ($cache_files as $cache_file)
    {
        $cache_size += filesize($cache_file);
    }
    $cache_size = size_format($cache_size);
    echo '<div class="wrap">';
    echo '<h1>Cache Stats</h1>';
    echo '<p>Number of cached pages: ' . $cache_count . '</p>';
    echo '<p>Total cache size: ' . $cache_size . '</p>';
    echo '<form method="post">';
    echo '<input type="submit" name="clean_cache" value="Clean Cache" class="button button-primary">';
    echo '</form>';
    echo '</div>';
}

// Clean cache
add_action('admin_init', 'clean_cache');

function clean_cache()
{
    if (isset($_POST['clean_cache']))
    {
        $cache_path = WP_CONTENT_DIR . '/cache/';
        $cache_files = glob($cache_path . '*.html');
        foreach ($cache_files as $cache_file)
        {
            unlink($cache_file);
        }
        wp_redirect(admin_url('options-general.php?page=cache-stats'));
    }
}

// Add cache stats in WordPress top bar
add_action('admin_bar_menu', 'add_cache_stats_in_admin_bar', 100);

function add_cache_stats_in_admin_bar($wp_admin_bar)
{
    $cache_path = WP_CONTENT_DIR . '/cache/';
    $cache_files = glob($cache_path . '*.html');
    $cache_count = count($cache_files);
    $cache_size = 0;
    foreach ($cache_files as $cache_file)
    {
        $cache_size += filesize($cache_file);
    }
    $cache_size = size_format($cache_size);
    $args = array(
        'id' => 'cache-stats',
        'title' => 'Cache Stats',
        'meta' => array(
            'class' => 'cache-stats',
            'title' => 'Cache Stats'
        )
    );
    $wp_admin_bar->add_node($args);
    $args = array(
        'id' => 'cache-stats-number',
        'title' => 'Number of cached pages: ' . $cache_count,
        'parent' => 'cache-stats',
        'meta' => array(
            'class' => 'cache-stats-number',
            'title' => 'Number of cached pages: ' . $cache_count
        )
    );
    $wp_admin_bar->add_node($args);
    $args = array(
        'id' => 'cache-stats-size',
        'title' => 'Total cache size: ' . $cache_size,
        'parent' => 'cache-stats',
        'meta' => array(
            'class' => 'cache-stats-size',
            'title' => 'Total cache size: ' . $cache_size
        )
    );
    $wp_admin_bar->add_node($args);
}

// Clean cache after 7 days
add_action('init', 'clean_cache_after_7_days');

function clean_cache_after_7_days()
{
    $cache_path = WP_CONTENT_DIR . '/cache/';
    $cache_files = glob($cache_path . '*.html');
    foreach ($cache_files as $cache_file)
    {
        if (filemtime($cache_file) < time() - 604800)
        {
            unlink($cache_file);
        }
    }
}