McAfee Antivirus 7.0 Information check

Hi, sorry to bother....
But I'd be very glad if you could posiblly help me
You had a script regarding to McAfee antivirus version, so I'd like the same but using it for Sophos Antivirus
and I'm new to scripts, so would you PLEASE tell me word what this means $tvd -> keyexist('HKLM\SOFTWARE\Network Associates\NetShield NT'), then you have $datnum -> $datnum=substr(readvalue($mcafee, ($mcafee,'szVirDefVer'),5,4) and so on
taken from your script
keyexist('HKLM\SOFTWARE\Network Associates\NetShield NT')
$datnum=substr(readvalue($mcafee,'szVirDefVer'),5,4)
$engine=readvalue($mcafee,'szEngineVer')
$product=readvalue($mcafee,'szProductVer')
Thank you very very much in advance
Boggi