Variáveis constantes do Joomla 1.5

JPATH_ADMINISTRATOR	The path to the administrator folder.
JPATH_BASE	The path to the installed Joomla! site.
JPATH_CACHE	The path to the cache folder.
JPATH_COMPONENT	The path to the current component being executed.
JPATH_COMPONENT_ADMINISTRATOR	The path to the administration folder of the current component being executed.
JPATH_COMPONENT_SITE	The path to the site folder of the current component being executed.
JPATH_CONFIGURATION	The path to folder containing the configuration.php file.
JPATH_INSTALLATION	The path to the installation folder.
JPATH_LIBRARIES	The path to the libraries folder.
JPATH_PLUGINS	The path to the plugins folder.
JPATH_ROOT	The path to the installed Joomla! site.
JPATH_SITE	The path to the installed Joomla! site.
JPATH_THEMES	The path to the templates folder.
JPATH_XMLRPC	The path to the XML-RPC Web service folder.(1.5 only)

fonte : http://docs.joomla.org/Constants

 Neste exemplo, o local de URI Joomla é mostrado com ambos os valores do argumento:

echo 'Joomla base URI is ' . JURI::base() . "\n";
echo 'Joomla base URI (path only) is ' . JURI::base( true ) . "\n";

fonte : http://docs.joomla.org/JURI/base