<?xml version="1.0" encoding="UTF-8"?> <form addfieldprefix="Joomla\CMS\Installation\Form\Field" addruleprefix="Joomla\CMS\Installation\Form\Rule"> <fieldset> <field name="language" type="installation.language" label="INSTL_LANGUAGE_LABEL" default="en-GB" required="true" onchange="Install.setlanguage();" /> </fieldset> </form>