ing_master_config() {
		if ( is_null( self::$is_using_master_config ) ) {
			if ( !Util_Environment::is_wpmu() ) {
				self::$is_using_master_config = true;
			} elseif ( is_network_admin() ) {
				self::$is_using_master_config = true;
			} else {
				$blog_data = Util_WpmuBlogmap::get_current_blog_data();
				if ( is_null( $blog_data ) ) {
					self::$is_using_master_config = true;
				} else {
					self::$is_using_master_config = ( $blog_data[0] == 'm' );
				}
			}
		}

		return self::$is_using_master_config;
	}

	/**
	 * Returns header W3TC adds to responses powered by itself
	 */
	static public function w3tc_header() {
		return W3TC_POWERED_BY .
			'/' . W3TC_VERSION;
	}

	/**
	 * Check if URL is valid
	 *
	 * @param string  $url
	 * @return boolean
	 */
	static public function is_url( $url ) {
		return preg_match( '~^(https?:)?//~', $url );
	}

	/**
	 * Returns true if current connection is secure
	 *
	 * @return boolean
	 */
	static public function is_https() {
		switch ( true ) {
		case ( isset( $_SERVER['HTTPS'] ) &&
				Util_Environment::to_boolean( $_SERVER['HTTPS'] ) ):
		case ( isset( $_SERVER['SERVER_PORT'] ) &&
				(int) $_SERVER['SERVER_PORT'] == 443 ):
		case ( isset( $_SERVER['HTTP_X_FORWARDED_PROTO'] ) &&
				$_SERVER['HTTP_X_FORWARDED_PROTO'] == 'https' ):
			return true;
		}

		return false;
	}

	/**
	 * Moves user to preview-mode or opposite
	 */
	static public function set_preview( $is_enabled ) {
		if ( $is_enabled )
			setcookie( 'w3tc_preview', '*', 0, '/' );
		else
			setcookie( "w3tc_preview", '', time()-3600, '/' );
	}

	/**
	 * Retuns true if preview settings active
	 *
	 * @return boolean
	 */
	static public function is_preview_mode() {
		return !empty( $_COOKIE['w3tc_preview'] );
	}

	/**
	 * Returns true if server is Apache
	 *
	 * @return boolean
	 */
	static public function is_apache() {
		// assume apache when unknown, since most common
		if ( empty( $_SERVER['SERVER_SOFTWARE'] ) )
			return true;

		return isset( $_SERVER['SERVER_SOFTWARE'] ) && stristr( $_SERVER['SERVER_SOFTWARE'], 'Apache' ) !== false;
	}

	/**
	 * Check whether server is LiteSpeed
	 *
	 * @return bool
	 */
	static public function is_litespeed() {
		return isset( $_SERVER['SERVER_SOFTWARE'] ) && stristr( $_SERVER['SERVER_SOFTWARE'], 'LiteSpeed' ) !== false;
	}

	/**
	 * Returns true if server is nginx
	 *
	 * @return boolean
	 */
	static public function is_nginx() {
		return isset( $_SERVER['SERVER_SOFTWARE'] ) && stristr( $_SERVER['SERVER_SOFTWARE'], 'nginx' ) !== false;
	}

	/**
	 * Returns true if server is nginx
	 *
	 * @return boolean
	 */
	static public function is_iis() {
		return isset( $_SERVER['SERVER_SOFTWARE'] ) && stristr( $_SERVER['SERVER_SOFTWARE'], 'IIS' ) !== false;
	}

	/**
	 * Returns domain from host
	 *
	 * @param string  $host
	 * @return string
	 */
	static public function url_to_host( $url ) {
		$a = parse_url( $url );
		if ( isset( $a['host'] ) )
			return $a['host'];

		return '';
	}

	/**
	 * Returns path from URL. Without trailing slash
	 */
	static public function url_to_uri( $url ) {
		$uri = @parse_url( $url, PHP_URL_PATH );

		// convert FALSE and other return values to string
		if ( empty( $uri ) )
			return '';

		return rtrim( $uri, '/' );
	}

	/**
	 * Returns current blog ID
	 *
	 * @return integer
	 */
	static public function blog_id() {
		global $w3_current_blog_id;

		if ( !is_null( $w3_current_blog_id ) )
			return $w3_current_blog_id;

		if ( !Util_Environment::is_wpmu() || is_network_admin() ) {
			$w3_current_blog_id = 0;
			return $w3_current_blog_id;
		}


		$blog_data = Util_WpmuBlogmap::get_current_blog_data();
		if ( !is_null( $blog_data ) ) {
			$w3_current_blog_id = substr( $blog_data, 1 );
		} else {
			$w3_current_blog_id = 0;
		}

		return $w3_current_blog_id;
	}

	/**
	 * Memoized version of wp_upload_dir. That function is quite slow
	 * for a number of times CDN calls it
	 */
	static public function wp_upload_dir() {
		static $values_by_blog = array();

		$blog_id = Util_Environment::blog_id();
		if ( !isset( $values_by_blog[$blog_id] ) )
			$values_by_blog[$blog_id] = wp_upload_dir();

		return $values_by_blog[$blog_id];
	}

	/**
	 * Returns path to section's cache dir
	 *
	 * @param string  $section
	 * @return string
	 */
	static public function cache_dir( $section ) {
		return W3TC_CACHE_DIR . DIRECTORY_SEPARATOR . $section;
	}

	/**
	 * Returns path to blog's cache dir
	 *
	 * @param string  $section
	 * @param null|int $blog_id
	 * @return string
	 */
	static public function cache_blog_dir( $section, $blog_id = null ) {
		if ( !Util_Environment::is_wpmu() )
			$postfix = '';
		else {
			if ( is_null( $blog_id ) )
				$blog_id = Util_Environment::blog_id();

			$postfix = DIRECTORY_SEPARATOR . sprintf( '%d', $blog_id );

			if ( defined( 'W3TC_BLOG_LEVELS' ) ) {
				for ( $n = 0; $n < W3TC_BLOG_LEVELS; $n++ )
					$postfix = DIRECTORY_SEPARATOR .
						substr( $postfix, strlen( $postfix ) - 1 - $n, 1 ) .
						$postfix;
			}
		}

		return Util_Environment::cache_dir( $section ) . $postfix;
	}

	static public function cache_blog_minify_dir() {
		// when minify manual used with a shared config - shared
		// minify urls has to be used too, since CDN upload is possible
		// only from network admin
		if ( Util_Environment::is_wpmu() &&
			Util_Environment::is_using_master_config() &&
			! Dispatcher::config()->get_boolean( 'minify.auto' ) )
			$path = Util_Environment::cache_blog_dir( 'minify', 0 );
		else
			$path = Util_Environment::cache_blog_dir( 'minify' );

		return $path;
	}



	/**
	 * Returns URL regexp from URL
	 *
	 * @param string  $url
	 * @return string
	 */
	static public function get_url_regexp( $url ) {
		$url = preg_replace( '~(https?:)?//~i', '', $url );
		$url = preg_replace( '~^www\.~i', '', $url );

		$regexp = '(https?:)?//(www\.)?' . Util_Environment::preg_quote( $url );

		return $regexp;
	}

	/**
	 * Returns SSL URL if current connection is https
	 *
	 * @param string  $url
	 * @return string
	 */
	static public function url_to_maybe_https( $url ) {
		if ( Util_Environment::is_https() ) {
			$url = str_replace( 'http://', 'https://', $url );
		}

		return $url;
	}

	/**
	 * Get domain URL
	 *
	 * @return string
	 */

	static public function home_domain_root_url() {
		$home_url = get_home_url();
		$parse_url = @parse_url( $home_url );

		if ( $parse_url && isset( $parse_url['scheme'] ) && isset( $parse_url['host'] ) ) {
			$scheme = $parse_url['scheme'];
			$host = $parse_url['host'];
			$port = ( isset( $parse_url['port'] ) && $parse_url['port'] != 80 ? ':' . (int) $parse_url['port'] : '' );
			$domain_url = sprintf( '%s://%s%s', $scheme, $host, $port );

			return $domain_url;
		}

		return false;
	}

	/**
	 * Returns domain url regexp
	 *
	 * @return string
	 */
	static public function home_domain_root_url_regexp() {
		$domain_url = Util_Environment::home_domain_root_url();
		$regexp = Util_Environment::get_url_regexp( $domain_url );

		return $regexp;
	}

	/**
	 * Returns SSL home url
	 *
	 * @return string
	 */
	static public function home_url_maybe_https() {
		$home_url = get_home_url();
		$ssl = Util_Environment::url_to_maybe_https( $home_url );

		return $ssl;
	}

	/**
	 * Returns home url regexp
	 *
	 * @return string
	 */
	static public function home_url_regexp() {
		$home_url = get_home_url();
		$regexp = Util_Environment::get_url_regexp( $home_url );

		return $regexp;
	}

	/**
	 * Copy of wordpress get_home_path, but accessible not only for wp-admin
	 * Get the absolute filesystem path to the root of the WordPress installation
	 * (i.e. filesystem path of siteurl)
	 *
	 * @return string Full filesystem path to the root of the WordPress installation
	 */
	static public function site_path() {
		$home    = set_url_scheme( get_option( 'home' ), 'http' );
		$siteurl = set_url_scheme( get_option( 'siteurl' ), 'http' );

		$home_path = ABSPATH;
		if ( ! empty( $home ) && 0 !== strcasecmp( $home, $siteurl ) ) {
			$wp_path_rel_to_home = str_ireplace( $home, '', $siteurl ); /* $siteurl - $home */
			// fix of get_home_path, used when index.php is moved outside of
			// wp folder.
			$pos = strripos(
				str_replace( '\\', '/', $_SERVER['SCRIPT_FILENAME'] ),
				trailingslashit( $wp_path_rel_to_home ) );
			if ( $pos !== false ) {
				$home_path = substr( $_SERVER['SCRIPT_FILENAME'], 0, $pos );
				$home_path = trailingslashit( $home_path );
			} else if ( defined( 'WP_CLI' ) ) {
				$pos = strripos(
					str_replace( '\\', '/', ABSPATH ),
					trailingslashit( $wp_path_rel_to_home ) );
				if ( $pos !== false ) {
					$home_path = substr( ABSPATH, 0, $pos );
					$home_path = trailingslashit( $home_path );
				}
			}
		}

		return str_replace( '\\', DIRECTORY_SEPARATOR, $home_path );
	}



	/**
	 * Returns absolute path to document root
	 *
	 * No trailing slash!
	 *
	 * @return string
	 */
	static public function document_root() {
		static $document_root = null;

		if ( !is_null( $document_root ) )
			return $document_root;

		$c = Dispatcher::config();
		$docroot_fix = $c->get_boolean( 'docroot_fix.enable' );

		if ( $docroot_fix ) {
			$document_root = untrailingslashit( ABSPATH );
			return $document_root;
		}

		if ( !empty( $_SERVER['SCRIPT_FILENAME'] ) &&
			!empty( $_SERVER['PHP_SELF'] ) ) {
			$script_filename = Util_Environment::normalize_path(
				$_SERVER['SCRIPT_FILENAME'] );
			$php_self = Util_Environment::normalize_path(
				$_SERVER['PHP_SELF'] );
			if ( substr( $script_filename, -strlen( $php_self ) ) == $php_self ) {
				$document_root = substr( $script_filename, 0, -strlen( $php_self ) );
				$document_root = realpath( $document_root );
				return $document_root;
			}
		}

		if ( !empty( $_SERVER['PATH_TRANSLATED'] ) ) {
			$document_root = substr(
				Util_Environment::normalize_path( $_SERVER['PATH_TRANSLATED'] ),
				0,
				-strlen( Util_Environment::normalize_path( $_SERVER['PHP_SELF'] ) ) );
		} elseif ( !empty( $_SERVER['DOCUMENT_ROOT'] ) ) {
			$document_root = Util_Environment::normalize_path( $_SERVER['DOCUMENT_ROOT'] );
		} else {
			$document_root = ABSPATH;
		}

		$document_root = realpath( $document_root );
		return $document_root;
	}

	/**
	 * Returns absolute path to blog install dir
	 *
	 * Example:
	 *
	 * DOCUMENT_ROOT=/var/www/vhosts/domain.com
	 * install dir=/var/www/vhosts/domain.com/site/blog
	 * return /var/www/vhosts/domain.com/site/blog
	 *
	 * No trailing slash!
	 *
	 * @return string
	 */
	static public function site_root() {
		$site_root = ABSPATH;
		$site_root = realpath( $site_root );
		$site_root = Util_Environment::normalize_path( $site_root );

		return $site_root;
	}

	/**
	 * Returns blog path
	 *
	 * Example:
	 *
	 * siteurl=http://domain.com/site/blog
	 * return /site/blog/
	 *
	 * With trailing slash!
	 *
	 * @return string
	 */
	static public function site_url_uri() {
		return Util_Environment::url_to_uri( site_url() ) . '/';
	}

	/**
	 * Returns home domain
	 *
	 * @return string
	 */
	static public function home_url_host() {
		$home_url = get_home_url();
		$parse_url = @parse_url( $home_url );

		if ( $parse_url && isset( $parse_url['host'] ) ) {
			return $parse_url['host'];
		}

		return Util_Environment::host();
	}

	/**
	 * Returns home path
	 *
	 * Example:
	 *
	 * home=http://domain.com/site/
	 * siteurl=http://domain.com/site/blog
	 * return /site/
	 *
	 * With trailing slash!
	 *
	 * @return string
	 */
	static public function home_url_uri() {
		return Util_Environment::url_to_uri( get_home_url() ) . '/';
	}

	static public function network_home_url_uri() {
		$uri = network_home_url( '', 'relative' );

		/* There is a bug in WP where network_home_url can return
		 * a non-relative URI even though scheme is set to relative.
		 */
		if ( Util_Environment::is_url( $uri ) )
			$uri = parse_url( $uri, PHP_URL_PATH );

		if ( empty( $uri ) )
			return '/';

		return $uri;
	}

	/**
	 * Returns server hostname with port
	 *
	 * @return string
	 */
	static public function host_port() {
		static $host = null;

		if ( $host === null ) {
			if ( !empty( $_SERVER['HTTP_HOST'] ) ) {
				// HTTP_HOST sometimes is not set causing warning
				$host = $_SERVER['HTTP_HOST'];
			} else {
				$host = '';
			}
		}

		return $host;
	}

	static public function host() {
		$host_port = Util_Environment::host_port();

		$pos = strpos( $host_port, ':' );
		if ( $pos === false )
			return $host_port;

		return substr( $host_port, 0, $pos );
	}

	/**
	 * Returns WP config file path
	 *
	 * @return string
	 */
	static public function wp_config_path() {
		$search = array(
			ABSPATH . 'wp-config.php',
			dirname( ABSPATH ) . DIRECTORY_SEPARATOR . 'wp-config.php'
		);

		foreach ( $search as $path ) {
			if ( file_exists( $path ) ) {
				return $path;
			}
		}

		return false;
	}


	/**
	 * Parses path
	 *
	 * @param string  $path
	 * @return mixed
	 */
	static public function parse_path( $path ) {
		$path = str_replace( array(
				'%BLOG_ID%',
				'%POST_ID%',
				'%BLOG_ID%',
				'%HOST%'
			), array(
				( isset( $GLOBALS['blog_id'] ) && is_numeric( $GLOBALS['blog_id'] ) ? (int) $GLOBALS['blog_id'] : 0 ),
				( isset( $GLOBALS['post_id'] ) && is_numeric( $GLOBALS['post_id'] ) ?
					(int) $GLOBALS['post_id'] : 0 ),
				Util_Environment::blog_id(),
				Util_Environment::host()
			), $path );

		return $path;
	}

	/**
	 * Normalizes file name
	 *
	 * Relative to site root!
	 *
	 * @param string  $file
	 * @return string
	 */
	static public function normalize_file( $file ) {
		if ( Util_Environment::is_url( $file ) ) {
			if ( strstr( $file, '?' ) === false ) {
				$home_url_regexp = '~' . Util_Environment::home_url_regexp() . '~i';
				$file = preg_replace( $home_url_regexp, '', $file );
			}
		}

		if ( !Util_Environment::is_url( $file ) ) {
			$file = Util_Environment::normalize_path( $file );
			$file = str_replace( Util_Environment::site_root(), '', $file );
			$file = ltrim( $file, '/' );
		}

		return $file;
	}

	/**
	 * Normalizes file name for minify
	 *
	 * Relative to document root!
	 *
	 * @param string  $file
	 * @return string
	 */
	static public function normalize_file_minify( $file ) {
		if ( Util_Environment::is_url( $file ) ) {
			if ( strstr( $file, '?' ) === false ) {
				$domain_url_regexp = '~' . Util_Environment::home_domain_root_url_regexp() . '~i';
				$file = preg_replace( $domain_url_regexp, '', $file );
			}
		}

		if ( !Util_Environment::is_url( $file ) ) {
			$file = Util_Environment::normalize_path( $file );
			$file = str_replace( Util_Environment::document_root(), '', $file );
			$file = ltrim( $file, '/' );
		}

		return $file;
	}

	/**
	 * Normalizes file name for minify
	 * Relative to document root!
	 *
	 * @param string  $file
	 * @return string
	 */
	static public function url_to_docroot_filename( $url ) {
		$data = array(
			'home_url' => get_home_url(),
			'url' => $url
		);
		$data = apply_filters( 'w3tc_url_to_docroot_filename', $data );

		$home_url = $data['home_url'];
		$normalized_url = $data['url'];
		$normalized_url = Util_Environment::remove_query_all( $normalized_url );

		// cut protocol
		$normalized_url = preg_replace( '~^http(s)?://~', '//', $normalized_url );
		$home_url = preg_replace( '~^http(s)?://~', '//', $home_url );

		if ( substr( $normalized_url, 0, strlen( $home_url ) ) != $home_url ) {
			// not a home url, return unchanged since cant be
			// converted to filename
			return null;
		}

		$path_relative_to_home = str_replace( $home_url, '', $normalized_url );

		$home = set_url_scheme( get_option( 'home' ), 'http' );
		$siteurl = set_url_scheme( get_option( 'siteurl' ), 'http' );

		$home_path = rtrim( Util_Environment::site_path(), '/' );
		// adjust home_path if site is not is home
		if ( ! empty( $home ) && 0 !== strcasecmp( $home, $siteurl ) ) {
			// $siteurl - $home
			$wp_path_rel_to_home = rtrim( str_ireplace( $home, '', $siteurl ), '/' );
			if ( substr( $home_path, -strlen( $wp_path_rel_to_home ) ) ==
				$wp_path_rel_to_home ) {
				$home_path = substr( $home_path, 0, -strlen( $wp_path_rel_to_home ) );
			}
		}

		// common encoded characters
		$path_relative_to_home = str_replace( '%20', ' ', $path_relative_to_home );

		$full_filename = $home_path . DIRECTORY_SEPARATOR .
			trim( $path_relative_to_home, DIRECTORY_SEPARATOR );

		$docroot = Util_Environment::document_root();
		if ( substr( $full_filename, 0, strlen( $docroot ) ) == $docroot ) {
			$docroot_filename = substr( $full_filename, strlen( $docroot ) );
		} else {
			$docroot_filename = $path_relative_to_home;
		}

		// sometimes urls (coming from other plugins/themes)
		// contain multiple "/" like "my-folder//myfile.js" which
		// fails to recognize by filesystem, while url is accessible
		$docroot_filename = str_replace( '//', DIRECTORY_SEPARATOR, $docroot_filename );

		return ltrim( $docroot_filename, DIRECTORY_SEPARATOR );
	}

	static public function docroot_to_full_filename( $docroot_filename ) {
		return rtrim( Util_Environment::document_root(), DIRECTORY_SEPARATOR ) .
			DIRECTORY_SEPARATOR . $docroot_filename;
	}

	/**
	 * Translates remote file to local file
	 *
	 * @param string  $file
	 * @return string
	 */
	static public function translate_file( $file ) {
		return $file;
	}

	/**
	 * Removes WP query string from URL
	 */
	static public function remove_query( $url ) {
		$url = preg_replace( '~(\?|&amp;|&#038;|&)+ver=[a-z0-9-_\.]+~i', '', $url );

		return $url;
	}

	/**
	 * Removes all query strings from url
	 */
	static public function remove_query_all( $url ) {
		$pos = strpos( $url, '?' );
		if ( $pos === false )
			return $url;

		return substr( $url, 0, $pos );
	}


	/**
	 * Converts win path to unix
	 *
	 * @param string  $path
	 * @return string
	 */
	static public function normalize_path( $path ) {
		$path = preg_replace( '~[/\\\]+~', '/', $path );
		$path = rtrim( $path, '/' );

		return $path;
	}

	/**
	 * Returns real path of given path
	 *
	 * @param string  $path
	 * @return string
	 */
	static public function realpath( $path ) {
		$path = Util_Environment::normalize_path( $path );
		$parts = explode( '/', $path );
		$absolutes = array();

		foreach ( $parts as $part ) {
			if ( '.' == $part ) {
				continue;
			}
			if ( '..' == $part ) {
				array_pop( $absolutes );
			} else {
				$absolutes[] = $part;
			}
		}

		return implode( '/', $absolutes );
	}

	/**
	 * Returns real path of given path
	 *
	 * @param string  $path
	 * @return string
	 */
	static public function path_remove_dots( $path ) {
		$parts = explode( '/', $path );
		$absolutes = array();

		foreach ( $parts as $part ) {
			if ( '.' == $part ) {
				continue;
			}
			if ( '..' == $part ) {
				array_pop( $absolutes );
			} else {
				$absolutes[] = $part;
			}
		}

		return implode( '/', $absolutes );
	}

	/**
	 * Returns full URL from relative one
	 */
	static public function url_relative_to_full( $relative_url ) {
		$relative_url = Util_Environment::path_remove_dots( $relative_url );

		if (version_compare(PHP_VERSION, '5.4.7') < 0) {
			if ( substr( $relative_url, 0, 2) == '//' ) {
				$relative_url =
					( Util_Environment::is_https() ? 'https' : 'http' ) .
					':' . $relative_url;
			}
		}

		$rel = parse_url( $relative_url );
		// it's full url already
		if ( isset( $rel['scheme'] ) || isset( $rel['host'] ) )
			return $relative_url;

		if ( !isset( $rel['host'] ) ) {
			$home_parsed = parse_url( get_home_url() );
			$rel['host'] = $home_parsed['host'];
			if ( isset( $home_parsed['port'] ) ) {
				$rel['port'] = $home_parsed['port'];
			}
		}

		$scheme = isset( $rel['scheme'] ) ? $rel['scheme'] . '://' : '//';
		$host = isset( $rel['host'] ) ? $rel['host'] : '';
		$port = isset( $rel['port'] ) ? ':' . $rel['port'] : '';
		$path = isset( $rel['path'] ) ? $rel['path'] : '';
		$query = isset( $rel['query'] ) ? '?' . $rel['query'] : '';
		return "$scheme$host$port$path$query";
	}

	/**
	 * Redirects to URL
	 *
	 * @param string  $url
	 * @param array   $params
	 * @return string
	 */
	static public function redirect( $url = '', $params = array() ) {
		$url = Util_Environment::url_format( $url, $params );
		if ( function_exists( 'do_action' ) )
			do_action( 'w3tc_redirect' );

		@header( 'Location: ' . $url );
		exit();
	}

	/**
	 * Redirects to URL
	 *
	 * @param string  $url
	 * @param array   $params
	 *
	 * @return string
	 */
	static public function safe_redirect_temp( $url = '', $params = array(),
			$safe_redirect = false ) {
		$url = Util_Environment::url_format( $url, $params );
		if ( function_exists( 'do_action' ) ) {
			do_action( 'w3tc_redirect' );
		}

		$status_code = 302;

		$protocol = $_SERVER["SERVER_PROTOCOL"];
		if ( 'HTTP/1.1' === $protocol ) {
			$status_code = 307;
		}

		$text = get_status_header_desc( $status_code );
		if ( !empty( $text ) ) {
			$status_header = "$protocol $status_code $text";
			@header( $status_header, true, $status_code );
		}

		add_action( 'wp_safe_redirect_fallback', array(
			'\W3TC\Util_Environment', 'wp_safe_redirect_fallback' ) );

		@header( 'Cache-Control: no-cache' );
		wp_safe_redirect( $url, $status_code );
		exit();
	}

	static public function wp_safe_redirect_fallback( $url ) {
		return home_url( '?w3tc_repeat=invalid' );
	}

	/**
	 * Detects post ID
	 *
	 * @return integer
	 */
	static public function detect_post_id() {
		global $posts, $comment_post_ID, $post_ID;

		if ( $post_ID ) {
			return $post_ID;
		} elseif ( $comment_post_ID ) {
			return $comment_post_ID;
		} elseif ( ( is_single() || is_page() ) && is_array( $posts ) && isset( $posts[0]->ID ) ) {
			return $posts[0]->ID;
		} elseif ( isset( $posts->ID ) ) {
			return $posts->ID;
		} elseif ( isset( $_REQUEST['p'] ) ) {
			return (integer) $_REQUEST['p'];
		}

		return 0;
	}

	static public function instance_id() {
		if ( defined( 'W3TC_INSTANCE_ID' ) ) {
			return W3TC_INSTANCE_ID;
		}

		static $instance_id;

		if ( !isset( $instance_id ) ) {
			$config = Dispatcher::config();
			$instance_id = $config->get_integer( 'common.instance_id', 0 );
		}
		return $instance_id;
	}

	/**
	 *
	 *
	 * @var Config $config
	 * @return string
	 */
	static public function w3tc_edition( $config = null ) {
		if ( Util_Environment::is_w3tc_pro( $config ) &&  Util_Environment::is_w3tc_pro_dev() )
			return 'pro development';
		if ( Util_Environment::is_w3tc_pro( $config ) )
			return 'pro';
		return 'community';
	}

	/**
	 *
	 *
	 * @param Config  $config
	 * @return bool
	 */
	static public function is_w3tc_pro( $config = null ) {
		if ( defined( 'W3TC_PRO' ) && W3TC_PRO )
			return true;
		if ( defined( 'W3TC_ENTERPRISE' ) && W3TC_ENTERPRISE )
			return true;

		if ( is_object( $config ) ) {
			$plugin_type = $config->get_string( 'plugin.type' );

			if ( $plugin_type == 'pro' || $plugin_type == 'pro_dev' )
				return true;
		}

		return false;
	}

	/**
	 * Enable Pro Dev mode support
	 *
	 * @return bool
	 */
	static public function is_w3tc_pro_dev() {
		return defined( 'W3TC_PRO_DEV_MODE' ) && W3TC_PRO_DEV_MODE;
	}

	/**
	 * Quotes regular expression string
	 *
	 * @param string  $string
	 * @param string  $delimiter
	 * @return string
	 */
	static public function preg_quote( $string, $delimiter = '~' ) {
		$string = preg_quote( $string, $delimiter );
		$string = strtr( $string, array(
				' ' => '\ '
			) );

		return $string;
	}

	/**
	 * Returns true if zlib output compression is enabled otherwise false
	 *
	 * @return boolean
	 */
	static public function is_zlib_enabled() {
		return Util_Environment::to_boolean( ini_get( 'zlib.output_compression' ) );
	}

	/**
	 * Recursive strips slahes from the var
	 *
	 * @param mixed   $var
	 * @return mixed
	 */
	static public function stripslashes( $var ) {
		if ( is_string( $var ) ) {
			return stripslashes( $var );
		} elseif ( is_array( $var ) ) {
			$var = array_map( array( '\W3TC\Util_Environment', 'stripslashes' ), $var );
		}

		return $var;
	}

	/**
	 * Checks if post should be flushed or not. Returns true if it should not be flushed
	 *
	 * @param unknown $post
	 * @param string  $module which cache module to check against (pgcache, varnish, dbcache or objectcache)
	 * @param Config  $config
	 * @return bool
	 */
	static public function is_flushable_post( $post, $module, $config ) {
		if ( is_numeric( $post ) )
			$post = get_post( $post );
		$post_status = array( 'publish' );
		// dont flush when we have post "attachment"
		// its child of the post and is flushed always when post is published, while not changed in fact
		$post_type = array( 'revision', 'attachment' );
		switch ( $module ) {
		case 'pgcache':
		case 'varnish':
		case 'posts':   // means html content of post pages
			if ( !$config->get_boolean( 'pgcache.reject.logged' ) )
				$post_status[] = 'private';
			break;
		case 'dbcache':
			if ( !$config->get_boolean( 'dbcache.reject.logged' ) )
				$post_status[] = 'private';
			break;
		}

		$flushable = is_object( $post ) &&
			!in_array( $post->post_type, $post_type ) &&
			in_array( $post->post_status, $post_status );

		return apply_filters( 'w3tc_flushable_post', $flushable, $post, $module );
	}



	/**
	 * Checks if post belongs to a custom post type
	 *
	 * @since 2.1.7
	 * 
	 * @param unknown $post
	 *
	 * @return bool
	 */
	static public function is_custom_post_type( $post ) {
		$post_type = get_post_type_object( $post->post_type );

		// post type not found belongs to default post type(s)
		if ( empty ( $post_type ) )
			return false;
		
		// check if custom
		if ( $post_type->_builtin === false )
			return true;

		return false;
	}



	/**
	 * Converts value to boolean
	 *
	 * @param mixed   $value
	 * @return boolean
	 */
	static public function to_boolean( $value ) {
		if ( is_string( $value ) ) {
			switch ( strtolower( $value ) ) {
			case '+':
			case '1':
			case 'y':
			case 'on':
			case 'yes':
			case 'true':
			case 'enabled':
				return true;

			case '-':
			case '0':
			case 'n':
			case 'no':
			case 'off':
			case 'false':
			case 'disabled':
				return false;
			}
		}

		return (boolean) $value;
	}

	/**
	 * Returns the apache, nginx version
	 *
	 * @return string
	 */
	static public function get_server_version() {
		$sig = explode( '/', $_SERVER['SERVER_SOFTWARE'] );
		$temp = isset( $sig[1] ) ? explode( ' ', $sig[1] ) : array( '0' );
		$version = $temp[0];
		return $version;
	}

	/**
	 * Checks if current request is REST REQUEST
	 */
	static public function is_rest_request( $url ) {
		if ( defined( 'REST_REQUEST' ) && REST_REQUEST )
			return true;

		// in case when called before constant is set
		// wp filters are not available in that case
		return preg_match( '~' . W3TC_WP_JSON_URI . '~', $url );
	}

	static public function reset_microcache() {
		global $w3_current_blog_id;
		$w3_current_blog_id = null;

		self::$is_using_master_config = null;
	}
}