A collection of some of the best resources for learning php. Before starting, make sure you have a webserver, a database server running with php configured. There are quite a few integrated stacks readily available but in case unsure which one to pick, the easiest one perhaps is to setup XAMPP from Apache Friends.
This is almost always the best place to start if you are absolutely new to php. Provides a high level overview and introduction to basic syntax, talking to a database like mysql, utility functions, Ajax and more.
http://www.w3schools.com/PHP/DEfaULT.asP
Another getting started type tutorial is at http://in2.php.net/tut.php
It should be possible to setup and cover the contents of these tutorials in about 2 days, assuming you have exposure atleast 1 programming language.
Beyond the above tutorials a good collection of intermediate level topics are available at http://www.goodphptutorials.com/ . As the name suggests the collection is really good. It may not make sense to go through these start to end, but a quick review and then hitting a project with occassionally refering back to the topics may be much more efficient in terms of learnng. This is however, very subjective and depends on individual's learning style.
Beyond this a simple websearch works best to find pertitent resources.
Setting up an Integrated Development Environment may be useful and convenient. Eclipse PDTis a good alternative.