cachify.class.php

<?php

/**
* Cachify
*/
final class Cachify {

	/**
	 * Plugin options
	 *
	 * @since  2.0
	 * @var    array
	 */
	private static $options;

	/**
	 * Caching method
	 *
	 * @since  2.0
	 * @var    object
	 */
	private static $method;

	/**
	 * Whether we are on an Nginx server or not.
	 *
	 * @since 2.2.5
	 * @var   boolean
	 */
	private static $is_nginx;

	/**
	 * Method settings
	 *
	 * @since  2.0.9
	 * @var    integer
	 */
	const METHOD_DB = 0;
	const METHOD_APC = 1;
	const METHOD_HDD = 2;
	const METHOD_MMC = 3;

	/**
	 * Minify settings
	 *
	 * @since  2.0.9
	 * @var    integer
	 */
	const MINIFY_DISABLED = 0;
	const MINIFY_HTML_ONLY = 1;
	const MINIFY_HTML_JS = 2;

	/**
	 * Pseudo constructor
	 *
	 * @since   2.0.5
	 * @change  2.0.5
	 */
	public static function instance() {
		new self();
	}

	/**
	 * Constructor
	 *
	 * @since   1.0.0
	 * @change  2.2.2
	 *
	 * @param   void
	 * @return  void
	 */
	public function __construct() {
		/* Set defaults */
		self::_set_default_vars();

		if ( ! is_admin() && ! self::_skip_cache( true ) ) {
			/* Check whether there are cached data to be printed. */
			self::print_cache();
		}

		self::$is_nginx = $GLOBALS['is_nginx'];

		/* Publish hooks */
		add_action(
			'init',
			array(
				__CLASS__,
				'register_publish_hooks',
			),
			99
		);

		/* Flush Hooks */
		add_action(
			'cachify_remove_post_cache',
			array(
				__CLASS__,
				'remove_page_cache_by_post_id',
			)
		);

		add_action(
			'cachify_flush_cache',
			array(
				__CLASS__,
				'flush_total_cache',
			)
		);

		add_action(
			'_core_updated_successfully',
			array(
				__CLASS__,
				'flush_total_cache',
			)
		);

		add_action(
			'switch_theme',
			array(
				__CLASS__,
				'flush_total_cache',
			)
		);

		add_action(
			'wp_trash_post',
			array(
				__CLASS__,
				'flush_total_cache',
			)
		);

		/* Flush icon */
		add_action(
			'admin_bar_menu',
			array(
				__CLASS__,
				'add_flush_icon',
			),
			90
		);

		add_action(
			'init',
			array(
				__CLASS__,
				'process_flush_request',
			)
		);

		/* Flush (post) cache if comment is made from frontend or backend */
		add_action(
			'pre_comment_approved',
			array(
				__CLASS__,
				'pre_comment',
			),
			99,
			2
		);

		/* Backend */
		if ( is_admin() ) {
			add_action(
				'wpmu_new_blog',
				array(
					__CLASS__,
					'install_later',
				)
			);

			add_action(
				'delete_blog',
				array(
					__CLASS__,
					'uninstall_later',
				)
			);

			add_action(
				'admin_init',
				array(
					__CLASS__,
					'register_textdomain',
				)
			);

			add_action(
				'admin_init',
				array(
					__CLASS__,
					'register_settings',
				)
			);

			add_action(
				'admin_menu',
				array(
					__CLASS__,
					'add_page',
				)
			);

			add_action(
				'admin_enqueue_scripts',
				array(
					__CLASS__,
					'add_admin_resources',
				)
			);

			add_action(
				'transition_comment_status',
				array(
					__CLASS__,
					'touch_comment',
				),
				10,
				3
			);

			add_action(
				'edit_comment',
				array(
					__CLASS__,
					'edit_comment',
				)
			);

			add_filter(
				'dashboard_glance_items',
				array(
					__CLASS__,
					'add_dashboard_count',
				)
			);

			add_action(
				'post_submitbox_misc_actions',
				array(
					__CLASS__,
					'print_flush_dropdown',
				)
			);

			add_filter(
				'plugin_row_meta',
				array(
					__CLASS__,
					'row_meta',
				),
				10,
				2
			);

			add_filter(
				'plugin_action_links_' . CACHIFY_BASE,
				array(
					__CLASS__,
					'action_links',
				)
			);

			/* Frontend */
		} else {
			add_action(
				'template_redirect',
				array(
					__CLASS__,
					'manage_cache',
				),
				0
			);

			add_action(
				'robots_txt',
				array(
					__CLASS__,
					'robots_txt',
				)
			);
		}// End if().
	}

	/**
	 * Deactivation hook
	 *
	 * @since   2.1.0
	 * @change  2.1.0
	 */
	public static function on_deactivation() {
		self::flush_total_cache( true );
	}

	/**
	 * Activation hook
	 *
	 * @since   1.0
	 * @change  2.1.0
	 */
	public static function on_activation() {
		/* Multisite & Network */
		if ( is_multisite() && ! empty( $_GET['networkwide'] ) ) {
			/* Blog IDs */
			$ids = self::_get_blog_ids();

			/* Loop over blogs */
			foreach ( $ids as $id ) {
				switch_to_blog( $id );
				self::_install_backend();
			}

			/* Switch back */
			restore_current_blog();

		} else {
			self::_install_backend();
		}
	}

	/**
	 * Plugin installation on new MU blog.
	 *
	 * @since   1.0
	 * @change  1.0
	 *
	 * @param integer $id  Blog ID.
	 */
	public static function install_later( $id ) {
		/* No network plugin */
		if ( ! is_plugin_active_for_network( CACHIFY_BASE ) ) {
			return;
		}

		/* Switch to blog */
		switch_to_blog( $id );

		/* Install */
		self::_install_backend();

		/* Switch back */
		restore_current_blog();
	}

	/**
	 * Actual installation of the options
	 *
	 * @since   1.0
	 * @change  2.0
	 */
	private static function _install_backend() {
		add_option(
			'cachify',
			array()
		);

		/* Flush */
		self::flush_total_cache( true );
	}

	/**
	 * Uninstalling of the plugin per MU blog.
	 *
	 * @since   1.0
	 * @change  2.1.0
	 */
	public static function on_uninstall() {
		/* Global */
		global $wpdb;

		/* Multisite & Network */
		if ( is_multisite() && ! empty( $_GET['networkwide'] ) ) {
			/* Alter Blog */
			$old = $wpdb->blogid;

			/* Blog IDs */
			$ids = self::_get_blog_ids();

			/* Loop */
			foreach ( $ids as $id ) {
				switch_to_blog( $id );
				self::_uninstall_backend();
			}

			/* Switch back */
			switch_to_blog( $old );
		} else {
			self::_uninstall_backend();
		}
	}

	/**
	 * Uninstalling of the plugin for MU and network.
	 *
	 * @since   1.0
	 * @change  1.0
	 *
	 * @param integer $id  Blog ID.
	 */
	public static function uninstall_later( $id ) {
		/* No network plugin */
		if ( ! is_plugin_active_for_network( CACHIFY_BASE ) ) {
			return;
		}

		/* Switch to blog */
		switch_to_blog( $id );

		/* Install */
		self::_uninstall_backend();

		/* Switch back */
		restore_current_blog();
	}

	/**
	 * Actual uninstalling of the plugin
	 *
	 * @since   1.0
	 * @change  1.0
	 */
	private static function _uninstall_backend() {
		/* Option */
		delete_option( 'cachify' );

		/* Flush cache */
		self::flush_total_cache( true );
	}

	/**
	 * Get IDs of installed blogs
	 *
	 * @since   1.0
	 * @change  1.0
	 *
	 * @return  array  Blog IDs
	 */
	private static function _get_blog_ids() {
		/* Global */
		global $wpdb;

		return $wpdb->get_col( "SELECT blog_id FROM `$wpdb->blogs`" );
	}

	/**
	 * Set default options
	 *
	 * @since   2.0
	 * @change  2.0.7
	 */
	private static function _set_default_vars() {
		/* Options */
		self::$options = self::_get_options();

		/* APC */
		if ( self::METHOD_APC === self::$options['use_apc'] && Cachify_APC::is_available() ) {
			self::$method = new Cachify_APC;

			/* HDD */
		} elseif ( self::METHOD_HDD === self::$options['use_apc'] && Cachify_HDD::is_available() ) {
			self::$method = new Cachify_HDD;

			/* MEMCACHED */
		} elseif ( self::METHOD_MMC === self::$options['use_apc'] && Cachify_MEMCACHED::is_available() ) {
			self::$method = new Cachify_MEMCACHED;

			/* DB */
		} else {
			self::$method = new Cachify_DB;
		}
	}

	/**
	 * Get options
	 *
	 * @since   2.0
	 * @change  2.1.2
	 *
	 * @return  array  Array of option values
	 */
	private static function _get_options() {
		return wp_parse_args(
			get_option( 'cachify' ),
			array(
				'only_guests'	 	=> 1,
				'compress_html'	 	=> self::MINIFY_DISABLED,
				'cache_expires'	 	=> 12,
				'without_ids'	 	=> '',
				'without_agents' 	=> '',
				'use_apc'		 	=> self::METHOD_DB,
				'reset_on_comment'  => 0,
			)
		);
	}

	/**
	 * Modify robots.txt
	 *
	 * @since   1.0
	 * @change  2.1.9
	 *
	 * @param   string $data  Original content of dynamic robots.txt.
	 * @return  string        Modified content of robots.txt.
	 */
	public static function robots_txt( $data ) {
		/* HDD only */
		if ( self::METHOD_HDD !== self::$options['use_apc'] ) {
			return $data;
		}

		/* Path */
		$path = wp_parse_url( site_url(), PHP_URL_PATH );

		/* Output */
		$data .= sprintf(
			'%2$sDisallow: %1$s/wp-content/cache/cachify/%2$s',
			( empty( $path ) ? '' : $path ),
			PHP_EOL
		);

		return $data;
	}

	/**
	 * Add the action links
	 *
	 * @since   1.0
	 * @change  1.0
	 *
	 * @param   array $data  Initial array with action links.
	 * @return  array        Merged array with action links.
	 */
	public static function action_links( $data ) {
		/* Permissions? */
		if ( ! current_user_can( 'manage_options' ) ) {
			return $data;
		}

		return array_merge(
			$data,
			array(
				sprintf(
					'<a href="%s">%s</a>',
					add_query_arg(
						array(
							'page' => 'cachify',
						),
						admin_url( 'options-general.php' )
					),
					esc_html__( 'Settings', 'cachify' )
				)
			)
		);
	}

	/**
	 * Meta links of the plugin
	 *
	 * @since   0.5
	 * @change  2.0.5
	 *
	 * @param   array  $input  Initial array with meta links.
	 * @param   string $page   Current page.
	 * @return  array          Merged array with meta links.
	 */
	public static function row_meta( $input, $page ) {
		/* Permissions */
		if ( CACHIFY_BASE !== $page ) {
			return $input;
		}

		return array_merge(
			$input,
			array(
				'<a href="https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=8CH5FPR88QYML" target="_blank" rel="noopener noreferrer">' . esc_html__( 'Donate', 'cachify' ) . '</a>',
				'<a href="https://wordpress.org/support/plugin/cachify" target="_blank" rel="noopener noreferrer">' . esc_html__( 'Support', 'cachify' ) . '</a>',
			)
		);
	}

	/**
	 * Add cache properties to dashboard
	 *
	 * @since   2.0.0
	 * @change  2.2.2
	 *
	 * @param   array $items  Initial array with dashboard items.
	 * @return  array         Merged array with dashboard items.
	 */
	public static function add_dashboard_count( $items = array() ) {
		/* Skip */
		if ( ! current_user_can( 'manage_options' ) ) {
			return $items;
		}

		/* Cache size */
		$size = self::get_cache_size();

		/* Caching method */
		$method = call_user_func(
			array(
				self::$method,
				'stringify_method',
			)
		);

		/* Output of the cache size */
		$cachesize = ( 0 === $size )
			? esc_html__( 'Empty Cache', 'cachify' ) :
			/* translators: %s: cache size */
			sprintf( esc_html__( '%s Cache', 'cachify' ), size_format( $size ) );

		/* Right now item */
		$items[] = sprintf(
			'<a href="%s" title="%s: %s" class="cachify-glance">
            <svg class="cachify-icon cachify-icon--%s" aria-hidden="true" role="img">
                <use href="%s#cachify-icon-%s" xlink:href="%s#cachify-icon-%s">
            </svg> %s</a>',
			add_query_arg(
				array(
					'page' => 'cachify',
				),
				admin_url( 'options-general.php' )
			),
			esc_attr( strtolower( $method ) ),
			esc_html__( 'Caching method', 'cachify' ),
			esc_attr( $method ),
			plugins_url( 'images/symbols.svg', CACHIFY_FILE ),
			esc_attr( strtolower( $method ) ),
			plugins_url( 'images/symbols.svg', CACHIFY_FILE ),
			esc_attr( strtolower( $method ) ),
			$cachesize
		);

		return $items;
	}

	/**
	 * Get the cache size
	 *
	 * @since   2.0.6
	 * @change  2.0.6
	 *
	 * @return  integer    Cache size in bytes.
	 */
	public static function get_cache_size() {
		if ( ! $size = get_transient( 'cachify_cache_size' ) ) {
			/* Read */
			$size = (int) call_user_func(
				array(
					self::$method,
					'get_stats',
				)
			);

			/* Save */
			set_transient(
				'cachify_cache_size',
				$size,
				60 * 15
			);
		}

		return $size;
	}

	/**
	 * Add flush icon to admin bar menu
	 *
	 * @since   1.2
	 * @change  2.2.2
	 *
	 * @hook    mixed   cachify_user_can_flush_cache
	 *
	 * @param   object $wp_admin_bar  Object of menu items.
	 */
	public static function add_flush_icon( $wp_admin_bar ) {
		/* Quit */
		if ( ! is_admin_bar_showing() || ! apply_filters( 'cachify_user_can_flush_cache', current_user_can( 'manage_options' ) ) ) {
			return;
		}

		/* Display the admin icon anytime */
		echo '<style>#wp-admin-bar-cachify{display:list-item !important} #wp-admin-bar-cachify .ab-icon{margin:0 !important} #wp-admin-bar-cachify .ab-icon:before{content:"\f182";top:2px;margin:0}</style>';

		/* Add menu item */
		$wp_admin_bar->add_menu(
			array(
				'id' 	 => 'cachify',
				'href'   => wp_nonce_url( add_query_arg( '_cachify', 'flush' ), '_cachify__flush_nonce' ), // esc_url in /wp-includes/class-wp-admin-bar.php#L438.
				'parent' => 'top-secondary',
				'title'	 => '<span class="ab-icon dashicons"></span>',
				'meta'   => array(
					'title' => esc_html__( 'Flush the cachify cache', 'cachify' ),
				),
			)
		);
	}

	/**
	 * Process plugin's meta actions
	 *
	 * @since   0.5
	 * @change  2.2.2
	 *
	 * @hook    mixed  cachify_user_can_flush_cache
	 *
	 * @param   array $data  Metadata of the plugin.
	 */
	public static function process_flush_request( $data ) {
		/* Skip if not a flush request */
		if ( empty( $_GET['_cachify'] ) || 'flush' !== $_GET['_cachify'] ) {
			return;
		}

		/* Check nonce */
		if ( empty( $_GET['_wpnonce'] ) || ! wp_verify_nonce( $_GET['_wpnonce'], '_cachify__flush_nonce' ) ) {
			return;
		}

		/* Skip if not necessary */
		if ( ! is_admin_bar_showing() || ! apply_filters( 'cachify_user_can_flush_cache', current_user_can( 'manage_options' ) ) ) {
			return;
		}

		/* Load on demand */
		if ( ! function_exists( 'is_plugin_active_for_network' ) ) {
			require_once( ABSPATH . 'wp-admin/includes/plugin.php' );
		}

		/* Multisite & Network */
		if ( is_multisite() && is_plugin_active_for_network( CACHIFY_BASE ) ) {
			/* Old blog */
			$old = $GLOBALS['wpdb']->blogid;

			/* Blog IDs */
			$ids = self::_get_blog_ids();

			/* Loop over blogs */
			foreach ( $ids as $id ) {
				switch_to_blog( $id );
				self::flush_total_cache();
			}

			/* Switch back to old blog */
			switch_to_blog( $old );

			/* Notice */
			if ( is_admin() ) {
				add_action(
					'network_admin_notices',
					array(
						__CLASS__,
						'flush_notice',
					)
				);
			}
		} else {
			/* Flush cache */
			self::flush_total_cache();

			/* Notice */
			if ( is_admin() ) {
				add_action(
					'admin_notices',
					array(
						__CLASS__,
						'flush_notice',
					)
				);
			}
		}// End if().

		if ( ! is_admin() ) {
			wp_safe_redirect(
				remove_query_arg(
					'_cachify',
					wp_get_referer()
				)
			);

			exit();
		}
	}

	/**
	 * Notice after successful flushing of the cache
	 *
	 * @since   1.2
	 * @change  2.2.2
	 *
	 * @hook    mixed  cachify_user_can_flush_cache
	 */
	public static function flush_notice() {
		/* No admin */
		if ( ! is_admin_bar_showing() || ! apply_filters( 'cachify_user_can_flush_cache', current_user_can( 'manage_options' ) ) ) {
			return false;
		}

		echo sprintf(
			'<div class="notice notice-success is-dismissible"><p>%s</p></div>',
			esc_html__( 'Cachify cache is flushed.', 'cachify' )
		);
	}

	/**
	 * Remove page from cache or flush on comment edit
	 *
	 * @since   0.1.0
	 * @change  2.1.2
	 *
	 * @param   integer $id  Comment ID.
	 */
	public static function edit_comment( $id ) {
		if ( self::$options['reset_on_comment'] ) {
			self::flush_total_cache();
		} else {
			self::remove_page_cache_by_post_id(
				get_comment( $id )->comment_post_ID
			);
		}
	}

	/**
	 * Remove page from cache or flush on new comment
	 *
	 * @since   0.1.0
	 * @change  2.1.2
	 *
	 * @param   mixed $approved  Comment status.
	 * @param   array $comment   Array of properties.
	 * @return  mixed            Comment status.
	 */
	public static function pre_comment( $approved, $comment ) {
		/* Approved comment? */
		if ( 1 === $approved ) {
			if ( self::$options['reset_on_comment'] ) {
				self::flush_total_cache();
			} else {
				self::remove_page_cache_by_post_id( $comment['comment_post_ID'] );
			}
		}

		return $approved;
	}

	/**
	 * Remove page from cache or flush on comment edit
	 *
	 * @since   0.1
	 * @change  2.1.2
	 *
	 * @param   string $new_status  New status.
	 * @param   string $old_status  Old status.
	 * @param   object $comment     The comment.
	 */
	public static function touch_comment( $new_status, $old_status, $comment ) {
		if ( $new_status !== $old_status ) {
			if ( self::$options['reset_on_comment'] ) {
				self::flush_total_cache();
			} else {
				self::remove_page_cache_by_post_id( $comment->comment_post_ID );
			}
		}
	}

	/**
	 * Generate publish hook for custom post types
	 *
	 * @since   2.1.7  Make the function public
	 * @since   2.0.3
	 *
	 * @param   void
	 * @return  void
	 */
	public static function register_publish_hooks() {
		/* Available post types */
		$post_types = get_post_types(
			array(
				'public' => true,
			)
		);

		/* Empty data? */
		if ( empty( $post_types ) ) {
			return;
		}

		/* Loop the post types */
		foreach ( $post_types as $post_type ) {
			add_action(
				'publish_' . $post_type,
				array(
					__CLASS__,
					'publish_post_types',
				),
				10,
				2
			);
			add_action(
				'publish_future_' . $post_type,
				array(
					__CLASS__,
					'flush_total_cache',
				)
			);
		}
	}

	/**
	 * Removes the post type cache on post updates
	 *
	 * @since   2.0.3
	 * @change  2.2.2
	 *
	 * @param   integer $post_id  Post ID.
	 * @param   object  $post     Post object.
	 */
	public static function publish_post_types( $post_id, $post ) {
		/* No post_id? */
		if ( empty( $post_id ) || empty( $post ) ) {
			return;
		}

		/* Post status check */
		if ( ! in_array( $post->post_status, array( 'publish', 'future' ), true ) ) {
			return;
		}

		/* Check for post var AND flush */
		if ( ! isset( $_POST['_cachify_remove_post_type_cache_on_update'] ) ) {
			return self::flush_total_cache();
		}

		/* Check nonce */
		if ( ! isset( $_POST[ '_cachify__status_nonce_' . $post_id ] ) || ! wp_verify_nonce( $_POST[ '_cachify__status_nonce_' . $post_id ], CACHIFY_BASE ) ) {
			return;
		}

		/* Check user role */
		if ( ! current_user_can( 'publish_posts' ) ) {
			return;
		}

		/* Save as var */
		$remove_post_type_cache = (int) $_POST['_cachify_remove_post_type_cache_on_update'];

		/* Save as user meta */
		update_user_meta(
			get_current_user_id(),
			'_cachify_remove_post_type_cache_on_update',
			$remove_post_type_cache
		);

		/* Remove cache OR flush */
		if ( $remove_post_type_cache ) {
			self::remove_page_cache_by_post_id( $post_id );
		} else {
			self::flush_total_cache();
		}
	}

	/**
	 * Removes a page (id) from cache
	 *
	 * @since   2.0.3
	 * @change  2.1.3
	 *
	 * @param   integer $post_id  Post ID.
	 */
	public static function remove_page_cache_by_post_id( $post_id ) {
		/* Value check */
		if ( ! $post_id = (int) $post_id ) {
			return;
		}

		/* Remove page by url */
		self::remove_page_cache_by_url(
			get_permalink( $post_id )
		);
	}

	/**
	 * Removes a page url from cache
	 *
	 * @since   0.1
	 * @change  2.1.3
	 *
	 * @param  string $url  Page URL.
	 */
	public static function remove_page_cache_by_url( $url ) {
		/* Value check */
		if ( ! $url = (string) $url ) {
			return;
		}

		call_user_func(
			array(
				self::$method,
				'delete_item',
			),
			self::_cache_hash( $url ),
			$url
		);
	}

	/**
	 * Get cache validity
	 *
	 * @since   2.0.0
	 * @change  2.1.7
	 *
	 * @return  integer    Validity period in seconds.
	 */
	private static function _cache_expires() {
		return HOUR_IN_SECONDS * self::$options['cache_expires'];
	}

	/**
	 * Get hash value for caching
	 *
	 * @since   0.1
	 * @change  2.0
	 *
	 * @param   string $url  URL to hash [optional].
	 * @return  string       Cachify hash value.
	 */
	private static function _cache_hash( $url = '' ) {
		$prefix = is_ssl() ? 'https-' : '';
		return md5(
			empty( $url ) ? ( $prefix . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'] ) : ( $prefix . wp_parse_url( $url, PHP_URL_HOST ) . wp_parse_url( $url, PHP_URL_PATH ) )
		) . '.cachify';
	}

	/**
	 * Split by comma
	 *
	 * @since   0.9.1
	 * @change  1.0
	 *
	 * @param   string $input  String to split.
	 * @return  array          Splitted values.
	 */
	private static function _preg_split( $input ) {
		return (array) preg_split( '/,/', $input, -1, PREG_SPLIT_NO_EMPTY );
	}

	/**
	 * Check for index page
	 *
	 * @since   0.6
	 * @change  1.0
	 *
	 * @return  boolean  TRUE if index
	 */
	private static function _is_index() {
		return basename( $_SERVER['SCRIPT_NAME'] ) !== 'index.php';
	}

	/**
	 * Check for mobile devices
	 *
	 * @since   0.9.1
	 * @change  2.2.2
	 *
	 * @return  boolean  TRUE if mobile
	 */
	private static function _is_mobile() {
		return ( strpos( TEMPLATEPATH, 'wptouch' ) || strpos( TEMPLATEPATH, 'carrington' ) || strpos( TEMPLATEPATH, 'jetpack' ) || strpos( TEMPLATEPATH, 'handheld' ) );
	}

	/**
	 * Check if user is logged in or marked
	 *
	 * @since   2.0.0
	 * @change  2.0.5
	 *
	 * @return  boolean  $diff  TRUE on "marked" users
	 */
	private static function _is_logged_in() {
		/* Logged in */
		if ( is_user_logged_in() ) {
			return true;
		}

		/* Cookie? */
		if ( empty( $_COOKIE ) ) {
			return false;
		}

		/* Loop */
		foreach ( $_COOKIE as $k => $v ) {
			if ( preg_match( '/^(wp-postpass|wordpress_logged_in|comment_author)_/', $k ) ) {
				return true;
			}
		}

		return false;
	}

	/**
	 * Define exclusions for caching
	 *
	 * @since   0.2
	 * @change  2.3.0
	 *
	 * @param   boolean..$base_check Check only if request vars are empty and
	 *                               whether to skip caching for logged users.
	 * @return  boolean              TRUE on exclusion
	 *
	 * @hook    boolean  cachify_skip_cache
	 */
	private static function _skip_cache( $base_check = false ) {

		/* Plugin options */
		$options = self::$options;

		/* Request vars */
		if ( ! empty( $_POST ) || ( ! empty( $_GET ) && get_option( 'permalink_structure' ) ) ) {
			return true;
		}

		/* Logged in */
		if ( $options['only_guests'] && self::_is_logged_in() ) {
			return true;
		}

		/* If base check only has been requested, stop here. */
		if ( $base_check ) {
			return false;
		}

		/* No cache hook */
		if ( apply_filters( 'cachify_skip_cache', false ) ) {
			return true;
		}

		/* Conditional Tags */
		if ( self::_is_index() || is_search() || is_404() || is_feed() || is_trackback() || is_robots() || is_preview() || post_password_required() ) {
			return true;
		}

		/* WooCommerce usage */
		if ( defined( 'DONOTCACHEPAGE' ) && DONOTCACHEPAGE ) {
			return true;
		}

		/* Mobile request */
		if ( self::_is_mobile() ) {
			return true;
		}

		/* Post IDs */
		if ( $options['without_ids'] && is_singular() ) {
			if ( in_array( $GLOBALS['wp_query']->get_queried_object_id(), self::_preg_split( $options['without_ids'] ), true ) ) {
				return true;
			}
		}

		/* User Agents */
		if ( $options['without_agents'] && isset( $_SERVER['HTTP_USER_AGENT'] ) ) {
			if ( array_filter( self::_preg_split( $options['without_agents'] ), create_function( '$a', 'return strpos($_SERVER["HTTP_USER_AGENT"], $a);' ) ) ) {
				return true;
			}
		}

		return false;
	}

	/**
	 * Minify HTML code
	 *
	 * @since   0.9.2
	 * @change  2.0.9
	 *
	 * @param   string $data  Original HTML code.
	 * @return  string        Minified code
	 *
	 * @hook    array   cachify_minify_ignore_tags
	 */
	private static function _minify_cache( $data ) {
		/* Disabled? */
		if ( ! self::$options['compress_html'] ) {
			return $data;
		}

		/* Avoid slow rendering */
		if ( strlen( $data ) > 700000 ) {
			return $data;
		}

		/* Ignore this html tags */
		$ignore_tags = (array) apply_filters(
			'cachify_minify_ignore_tags',
			array(
				'textarea',
				'pre',
			)
		);

		/* Add the script tag */
		if ( self::MINIFY_HTML_JS !== self::$options['compress_html'] ) {
			$ignore_tags[] = 'script';
		}

		/* Empty blacklist? | TODO: Make it better */
		if ( ! $ignore_tags ) {
			return $data;
		}

		/* Convert to string */
		$ignore_regex = implode( '|', $ignore_tags );

		/* Minify */
		$cleaned = preg_replace(
			array(
				'/<!--[^\[><](.*?)-->/s',
				'#(?ix)(?>[^\S ]\s*|\s{2,})(?=(?:(?:[^<]++|<(?!/?(?:' . $ignore_regex . ')\b))*+)(?:<(?>' . $ignore_regex . ')\b|\z))#',
			),
			array(
				'',
				' ',
			),
			$data
		);

		/* Fault */
		if ( strlen( $cleaned ) <= 1 ) {
			return $data;
		}

		return $cleaned;
	}

	/**
	 * Flush total cache
	 *
	 * @since   0.1
	 * @change  2.0
	 *
	 * @param bool $clear_all_methods  Flush all caching methods (default: FALSE).
	 */
	public static function flush_total_cache( $clear_all_methods = false ) {
		if ( $clear_all_methods ) {
			/* DB */
			Cachify_DB::clear_cache();

			/* APC */
			Cachify_APC::clear_cache();

			/* HDD */
			Cachify_HDD::clear_cache();

			/* MEMCACHED */
			Cachify_MEMCACHED::clear_cache();
		} else {
			call_user_func(
				array(
					self::$method,
					'clear_cache',
				)
			);
		}

		/* Transient */
		delete_transient( 'cachify_cache_size' );
	}

	/**
	 * Assign the cache
	 *
	 * @since   0.1
	 * @change  2.0
	 *
	 * @param   string $data  Content of the page.
	 * @return  string        Content of the page.
	 */
	public static function set_cache( $data ) {
		/* Empty? */
		if ( empty( $data ) ) {
			return '';
		}

		/* Save */
		call_user_func(
			array(
				self::$method,
				'store_item',
			),
			self::_cache_hash(),
			self::_minify_cache( $data ),
			self::_cache_expires()
		);

		return $data;
	}

	/**
	 * Retrieve cache contents if there are any.
	 * @since 2.3
	 */
	public static function print_cache() {

		/* Data present in cache */
		$cache = call_user_func(
			array(
				self::$method,
				'get_item',
			),
			self::_cache_hash()
		);

		/* Cache hit? */
		if ( ! empty( $cache ) ) {
			/* Process cache */
			call_user_func(
				array(
					self::$method,
					'print_cache',
				),
				$cache
			);
		}
	}

	/**
	 * Initialize buffering of output to get cache data (unless caching should
	 * be skipped).
	 *
	 * @since   0.1
	 * @change  2.3
	 */
	public static function manage_cache() {
		/* No caching? */
		if ( self::_skip_cache() ) {
			return;
		}

		ob_start( 'Cachify::set_cache' );
	}

	/**
	 * Register CSS
	 *
	 * @since   1.0
	 * @change  2.1.3
	 *
	 * @param   string $hook  Current hook.
	 */
	public static function add_admin_resources( $hook ) {
		/* Hooks check */
		if ( 'index.php' !== $hook && 'post.php' !== $hook ) {
			return;
		}

		/* Plugin data */
		$plugin_data = get_plugin_data( CACHIFY_FILE );

		/* Register css */
		switch ( $hook ) {
			case 'index.php':
				wp_enqueue_style(
					'cachify-dashboard',
					plugins_url( 'css/dashboard.min.css', CACHIFY_FILE ),
					array(),
					$plugin_data['Version']
				);
			break;

			case 'post.php':
				wp_enqueue_script(
					'cachify-post',
					plugins_url( 'js/post.min.js', CACHIFY_FILE ),
					array( 'jquery' ),
					$plugin_data['Version'],
					true
				);
			break;

			default:
			break;
		}
	}

	/**
	 * Display a combo select on post publish box
	 *
	 * @since   2.1.3
	 * @change  2.2.2
	 */
	public static function print_flush_dropdown() {
		/* Post page only */
		if ( empty( $GLOBALS['pagenow'] ) || 'post.php' !== $GLOBALS['pagenow'] ) {
			return;
		}

		/* Published posts only */
		if ( empty( $GLOBALS['post'] ) || ! is_object( $GLOBALS['post'] ) || 'publish' !== $GLOBALS['post']->post_status ) {
			return;
		}

		/* Check user role */
		if ( ! current_user_can( 'publish_posts' ) ) {
			return;
		}

		/* Security */
		wp_nonce_field( CACHIFY_BASE, '_cachify__status_nonce_' . $GLOBALS['post']->ID );

		/* Already saved? */
		$current_action = (int) get_user_meta(
			get_current_user_id(),
			'_cachify_remove_post_type_cache_on_update',
			true
		);

		/* Init vars */
		$dropdown_options = '';
		$available_options = array(
			esc_html__( 'Total cache', 'cachify' ),
			esc_html__( 'Page cache', 'cachify' ),
		);

		/* Select options */
		foreach ( $available_options as $key => $value ) {
			$dropdown_options .= sprintf(
				'<option value="%1$d" %3$s>%2$s</option>',
				$key,
				$value,
				selected( $key, $current_action, false )
			);
		}

		/* Output */
		echo sprintf(
			'<div class="misc-pub-section" style="border-top:1px solid #eee">
				<label for="cachify_status">
					%1$s: <span id="output-cachify-status">%2$s</span>
				</label>
				<a href="#" class="edit-cachify-status hide-if-no-js">%3$s</a>

				<div class="hide-if-js">
					<select name="_cachify_remove_post_type_cache_on_update" id="cachify_status">
						%4$s
					</select>

					<a href="#" class="save-cachify-status hide-if-no-js button">%5$s</a>
	 				<a href="#" class="cancel-cachify-status hide-if-no-js button-cancel">%6$s</a>
	 			</div>
			</div>',
			esc_html__( 'Remove', 'cachify' ),
			$available_options[ $current_action ],
			esc_html__( 'Edit', 'cachify' ),
			$dropdown_options,
			esc_html__( 'OK', 'cachify' ),
			esc_html__( 'Cancel', 'cachify' )
		);
	}

	/**
	 * Add options page
	 *
	 * @since   1.0
	 * @change  2.2.2
	 */
	public static function add_page() {
		add_options_page(
			__( 'Cachify', 'cachify' ),
			__( 'Cachify', 'cachify' ),
			'manage_options',
			'cachify',
			array(
				__CLASS__,
				'options_page',
			)
		);
	}

	/**
	 * Available caching methods
	 *
	 * @since  2.0.0
	 * @change 2.1.3
	 *
	 * @param  array $methods  Array of all available methods.
	 * @return array           Array of actually available methods.
	 */
	private static function _method_select() {
		/* Defaults */
		$methods = array(
			self::METHOD_DB  => esc_html__( 'Database', 'cachify' ),
			self::METHOD_APC => esc_html__( 'APC', 'cachify' ),
			self::METHOD_HDD => esc_html__( 'Hard disk', 'cachify' ),
			self::METHOD_MMC => esc_html__( 'Memcached', 'cachify' ),
		);

		/* APC */
		if ( ! Cachify_APC::is_available() ) {
			unset( $methods[1] );
		}

		/* Memcached? */
		if ( ! Cachify_MEMCACHED::is_available() ) {
			unset( $methods[3] );
		}

		/* HDD */
		if ( ! Cachify_HDD::is_available() ) {
			unset( $methods[2] );
		}

		return $methods;
	}

	/**
	 * Minify cache dropdown
	 *
	 * @since   2.1.3
	 * @change  2.1.3
	 *
	 * @return  array    Key => value array
	 */
	private static function _minify_select() {
		return array(
			self::MINIFY_DISABLED  => esc_html__( 'No minify', 'cachify' ),
			self::MINIFY_HTML_ONLY => esc_html__( 'HTML', 'cachify' ),
			self::MINIFY_HTML_JS   => esc_html__( 'HTML + Inline JavaScript', 'cachify' ),
		);
	}

	/**
	 * Register the language file
	 *
	 * @since   2.1.3
	 * @change  2.1.3
	 */
	public static function register_textdomain() {
		load_plugin_textdomain(
			'cachify',
			false,
			CACHIFY_DIR . '/lang'
		);
	}

	/**
	 * Register settings
	 *
	 * @since   1.0
	 * @change  1.0
	 */
	public static function register_settings() {
		register_setting(
			'cachify',
			'cachify',
			array(
				__CLASS__,
				'validate_options',
			)
		);
	}

	/**
	 * Validate options
	 *
	 * @since   1.0.0
	 * @change  2.1.3
	 *
	 * @param   array $data  Array of form values.
	 * @return  array        Array of validated values.
	 */
	public static function validate_options( $data ) {
		/* Empty data? */
		if ( empty( $data ) ) {
			return;
		}

		/* Flush cache */
		self::flush_total_cache( true );

		/* Notification */
		if ( self::$options['use_apc'] !== $data['use_apc'] && $data['use_apc'] >= self::METHOD_APC ) {
			add_settings_error(
				'cachify_method_tip',
				'cachify_method_tip',
				sprintf(
					'&#8505; %s',
					esc_html__( 'The server configuration file (e.g. .htaccess) needs to be adjusted. Please have a look at the Setup-Tab.', 'cachify' )
				),
				'updated'
			);
		}

		/* Return */
		return array(
			'only_guests'      => (int) ( ! empty( $data['only_guests'] )),
			'compress_html'    => (int) $data['compress_html'],
			'cache_expires'    => (int) ( isset( $data['cache_expires'] ) ? $data['cache_expires'] : self::$options['cache_expires'] ),
			'without_ids'      => (string) isset( $data['without_ids'] ) ? sanitize_text_field( $data['without_ids'] ) : '',
			'without_agents'   => (string) isset( $data['without_ids'] ) ? sanitize_text_field( $data['without_agents'] ) : '',
			'use_apc'          => (int) $data['use_apc'],
			'reset_on_comment' => (int) ( ! empty( $data['reset_on_comment'] )),
		);
	}

	/**
	 * Display options page
	 *
	 * @since   1.0
	 * @change  2.2.2
	 */
	public static function options_page() {
	?>

		<div class="wrap" id="cachify_settings">
			<h1>
				Cachify
			</h1>

			<form method="post" action="options.php">
				<?php settings_fields( 'cachify' ) ?>

				<?php $options = self::_get_options() ?>

				<?php /* Adds a navbar and includes the specific page */
				if ( self::METHOD_DB !== $options ['use_apc'] ) {
					$cachify_tabs = array(
					'settings'  => esc_html__( 'Settings', 'cachify' ),
									'setup' => esc_html__( 'Setup', 'cachify' ),
							);

					$current_tab = isset( $_GET['cachify_tab'] ) ? $_GET['cachify_tab'] : 'settings';

					echo '<h2 class="nav-tab-wrapper">';
					foreach ( $cachify_tabs as $tab => $name ) {
						$class = ($tab === $current_tab) ? ' nav-tab-active' : '';
						$link = "?page=cachify&cachify_tab=$tab";
						echo "<a class='nav-tab$class' href='$link'>$name</a>";
					}
					echo '</h2>';

					switch ( $current_tab ) {
						case 'settings' :
							include 'cachify.settings.php';
							break;
						case 'setup' :
							if ( self::METHOD_HDD === $options ['use_apc'] ) {
								if ( self::$is_nginx ) { include 'setup/cachify.hdd.nginx.php';
								} else { include 'setup/cachify.hdd.htaccess.php'; }
							} elseif ( self::METHOD_APC === $options ['use_apc'] ) {
								if ( self::$is_nginx ) { include 'setup/cachify.apc.nginx.php';
								} else { include 'setup/cachify.apc.htaccess.php'; }
							} elseif ( ( self::METHOD_MMC === $options ['use_apc']) && self::$is_nginx ) {include 'setup/cachify.memcached.nginx.php';
							}
							break;
					}
				} else { include 'cachify.settings.php'; }// End if().
				?>
			</form>
		</div><?php
	}
}