Environment::getVarPath() 

\nn\t3::Environment()->getVarPath(); 

Get the absolute path to the /var directory of Typo3.

This directory stores temporary cache files. Depending on the version of Typo3 and installation type (Composer or Non-Composer mode) this directory can be found in different locations.

// /full/path/to/typo3temp/var/
$path = \nn\t3::Environment()->getVarPath();

public function getVarPath() {
	return rtrim(\TYPO3\CMS\Core\Core\Environment::getVarPath(), '/').'/';
}