This question was raised on the Joomla General Development Google group list but I was unable to respond successfully (6 replies deleted - I obviously did something wrong) - so I thought I'd raise the questions here and answer them.

Q1 - In my install script I like to report to the user in a message what version of the component has just been installed/uninstalled. In J3 I read the version from the manifest file as the best source of truth thus:

$message = 'Installing xbOSM component v.' . $parent->get('manifest')->version . ' ' . $parent->get('manifest')->creationDate;

Factory::getApplication()->enqueueMessage($message, 'Info');

Q2 - with some components when installing I need to create a default category ('Uncategorised') for the component in the install script. Usually I create SQL insert, but is there another way that suits both J3 & J4?

  • Thanks for the corrections Mick. Cheers Commented Jul 3, 2021 at 6:42

1 Answer 1


Q1 - In J4 I found that this simple function gets what you might want:

 * Get the version of the component
 * @return version element of manifest
public static function getComponentVersion()
    $componentXML = Installer::parseXMLInstallFile(Path::clean(JPATH_ADMINISTRATOR . '/components/com_mycomponent/mycomponent.xml'));

    return $componentXML['version'];

Q2 - I use a separate function to create categories based on a passed array:

 * The extension name. This should be set in the installer script.
protected $extension = 'com_mycomponent';

 * method to run after an install/update/uninstall method
 * @return void
public function postflight($type, $parent)
    // $parent is the class calling this method
    // $type is the type of change (install, update or discover_install)
    // the variable $type was returning lowercase values, it must be uppercase
    $type = strtoupper($type);
    echo '<p>' . Text::_('COM_MYCOMONENT_POSTFLIGHT_' . $type . '_TEXT') . '</p>';

    // setup data for first time install
    if ($type == "INSTALL") {
        // Load categories
        $cattitles = array(
        $cat_id = $this->createCategory($cattitles);

    // Clear Joomla system cache.
    $cache = Factory::getCache();

* Function to create category records
* @param array category titles
* @param string category group or type
* @return void
public function createCategory($cat_titles)
    foreach ($cat_titles as $cat) {
        $category = Table::getInstance('Category');
        $category->extension = $this->extension;
        $category->title = $cat;
        $category->description = '';
        $category->published = 1;
        $category->access = 1;
        $category->params = '{"category_layout":"","image":"","image_alt":""}';
        $category->metadata = '{"page_title":"","author":"","robots":""}';
        $category->language = '*';

        // Set the location in the tree
        $category->setLocation(1, 'last-child');

        // Check to make sure our data is valid
        if (!$category->check()) {
            throw new Exception(500, $category->getError());
            return false;

        // Now store the category
        if (!$category->store(true)) {
            throw new Exception(500, $category->getError());
            return false;

    // Build the path for our category
    echo '<p>' . Text::_('Categories created') . '</p>';
    return $category->id;

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