Errors, warnings and notices can be displayed from any component, module, plugin or template. The messages use the standard bootstrap CSS styles for alerts.

// Get a handle to the Joomla! application object
$application = JFactory::getApplication();

// Add a message to the message queue
$application->enqueueMessage(JText::_('SOME_ERROR_OCCURRED'), 'error');

The second argument to the enqueueMessage function is the type of the message. The default is 'message', but 'error' results in a different style for the message.

Where it is displayed?

The message is displayed in place of a special jdoc:include statement in the template. Place the following in your template at the location where you want messages to appear:

<jdoc:include type="message" />