The @ ignores any error message made by the mkdir() function or any other function https://www.php.net/manual/en/language.operators.errorcontrol.php mkdir() will throw an error if the directory exist or if the permission was denied if you remove it, (you guessed it) any error made by the function won't be ignored btw why tf do people still do @mkdir($this->getDataFolder());
The @ supresses any warning and errors that might be generated. You can read more about it right here: https://www.php.net/manual/en/language.operators.errorcontrol.php from the PHP website ^^ (GG @mmm545 for being earlier xD)