Where to start?

Hi all, I am looking into learning PHP, I have a good understanding of HTML, JS and I know a little Perl. Firstly I know PHP is all server side and so a damn sight different from the above, but will they help me at all? Secondly where do I start? Are there any good on-line resources and or books that anyone knows? I am plannig to develop an E-comm solution us Oscommerce, does anyone know if this is any good or is naff? Any hints, tips or pointers would be greatly appreciated. Thanks, Simon