I've been a ASP.NET developer and started to I learn PHP about 3 months ago. I could quickly get familier to the language because of the video tutorials I practiced. Some of free video tutorials I practiced was video-tutes.com videos. PHP is not hard there are many free resources to learn it as its free.
Not free, but straight to the point and extremely useful are the PHP tutorial books written by Robert Plank. They've taught me more than all the free courses I tried before... (See a list of his products at his site at http://robertplank.com)
Learning PHP is always fun and free. My Suggestion is hands on tutorials of fun stuff your excited to see the end result. Use mIRC or xChat and idle in some php channel. The are tons of user there in any time zone that may answer questions on the fly or even post here. Join a PHP forum post questions if you get stuck. Always think logically when Programming, so if your stuck take a 10min break ask someone then try it again. Hope my advise helps thanks, krishmanohar :S
site php.net and sourceforge.net ... try to download php source code to study, that's my own PHP learning method
official PHP website has a manual will all expressions & syntax, its pretty useful! get yourslf there. it's probably best to look at some code first and try and get your head around it etc. PHP is very hands on, which makes it quite intresting really!
http://www.phpvideotutorials.com/ This site offers some free lessons. I found them very well done and you can also buy some advanced video tutorials.
Check out this PHP basics ebook - Not free, but only $2.50 for DPF forum members http://forums.digitalpoint.com/showthread.php?t=1101807