Constants

Every request defines these before anything else runs, in core/bootstrap/app.php. Extensions may rely on them anywhere.

You need them whenever you touch the filesystem. A hub's files are not necessarily under the code — the platform can sit outside the document root — so a path written as 'core/components/com_booking/…' or '/www/hub/app' works on the machine you wrote it on and nowhere else. Build every path from the constants instead.

Paths

All of these are absolute filesystem paths, not URLs, and none has a trailing separator.

Constant	Value
PATH_ROOT	The installation's root directory, the one holding core/ and app/.
PATH_CORE	The platform: PATH_ROOT/core. Components, plugins, modules, templates, and the framework libraries the release ships.
PATH_APP	One hub's own directory: PATH_ROOT/app. Its configuration, its overriding extensions and templates, its uploads, cache, and logs.
DS	DIRECTORY_SEPARATOR, so / on every platform Hubzero supports.

PATH_ROOT, PATH_CORE, and PATH_APP are only defined if nothing has defined them already. The site entry point sets PATH_ROOT from the web server's document root and reads PATH_CORE from the environment, which is how a deployment can keep the platform outside the document root.

Write paths by joining with DS, and never assume a hub's files live under the code:

$path = PATH_APP . DS . $resourcePath . DS . 'content' . DS . $name;

The same join appears in com_resources, which builds every media path this way rather than concatenating separators of its own:

		$new_file    = PATH_APP . DS . $resource_path . DS . 'presentation.json';

Version

HVERSION is the platform version as a string, currently

define('HVERSION', '2.4.1');

Entry guard

_HZEXEC_ is defined by the bootstrap and by nothing else. Files that must never be requested directly over HTTP open with a guard that stops them when it is absent:

defined('_HZEXEC_') or die();

Every view template and every file outside a class carries it. A file that only declares a namespaced class does not need it, because reaching it directly produces no output.

Legacy path aliases

The platform keeps an older set of path constants so that inherited code still resolves. New code should use the PATH_ constants above; these are listed for reading old extensions.

Alias	Same as
JPATH_ROOT, JPATH_BASE, JPATH_SITE	PATH_ROOT
JPATH_CONFIGURATION	PATH_APP/config
JPATH_THEMES	PATH_APP/templates
JPATH_CACHE	PATH_APP/cache
JPATH_LIBRARIES	PATH_CORE/libraries
JPATH_PLUGINS	PATH_CORE/plugins
JPATH_MANIFESTS	PATH_CORE/manifests
JPATH_ADMINISTRATOR	PATH_ROOT/administrator
JPATH_API	PATH_ROOT/api
JPATH_INSTALLATION	PATH_ROOT/installation

Locale

The bootstrap fixes the process locale before any extension runs: the default time zone is UTC and the internal encoding is UTF-8. Dates are stored and compared in UTC and converted for display, so do not change the default time zone. See Dates.