Understanding system multiple steps

So I am using system() to try and access sftp from my php scripts. How do I do multiple steps once I've initiated my command e.g. $file = 'filname.txt'; system( "C:\sftp\sftp.exe <login flags> | put ".$file ); Im on a windows box, so I don't know if I can do something like this ... anyway any help would be ppreciated THanks