\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::installExtension('my_extension');
\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::activateExtension('my_extension');
\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::deactivateExtension('my_extension');
$is_active = \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::isLoaded('my_extension');This utility package belongs to the TYPO3 CMS core, and it's part of the TYPO3\CMS\Core\Utility namespace. It's a library that is included with TYPO3 by default and doesn't require any additional installation.