Oxid variables abreviations/aliases

Hello. I’ve took a look on the code behind the shop and I find it confusing having different aliases on the variables that are not detailed anywhere. Can anyone explain me the role of “s”, “a”, “i”, “o” before the variables names?
$sSql, $oPayments, $aLanguages, $oLang, $iLanguageId and so on.

Thank you!

Hungarian notation.
s string a array i integer o object
Not used anymore in Oxid 6.


Thank you a lot!