how works ftp_ssl_connect?

hi all! i'm just playing around a bit with the ftp_ssl_connect funtion but i am not quite sure "what it is doing", maybe i am missunderstanding something completly! ;-) if i use the function ftp_ssl_connect to a ftp host (running vsftpd) listening on port 21 (and then ftp_login) all data is sent without any encryption (tested with ethereal) although there is a "REQUEST TLS/SSL" via USER and PASS. then i used ftp_ssl_connect with port 22 (if i use sftp it works and everything runs over port 22). but with php i could not get a connection. in /var/log/messages it says: ---8<--- Did not receive identification string from ::ffff:141.61.1.25 --->8--- what now?? or is this function not for use with the sftp-server from the ssh-package? thanks for any hints! markus