Hi all, I would like to learn Drupal from scratch. Could somebody tell me how much PHP knowledge is required to study Drupal thoroughly and how long it will take to become a drupal expert!!! Thank you all.
you want to become a module expert or a theme designer?... for theming drupal template limited php skill is enough.
If you want a good book about druapl development try this one: http://www.amazon.com/Pro-Drupal-7-Development-Third/dp/1430228385/ref=sr_1_4?ie=UTF8&s=books&qid=1262975753&sr=8-4
most people I know need at least 3 months to get used to it. and at least 6 months to master it for an intro, you don't need to be an expert in PHP, you only need to know the right modules to use for your projects.
For just setting up a website and "using" Drupal, you dont need to know nuthin 'bout no PHP.. i started using Drupal with zero PHP knowledge and had my site up and running in just a few hours, dialed-in within a week or so..
To the OP, as Tearabite said, just to build a site in Drupal requires no knowledge of PHP. And you can get pretty far in Drupal without ever having to learn a lick of PHP. If you want to develop your own themes, then you will need some beginner to intermediate PHP skills, and this is knowledge that you can easily pick up by following basic PHP tutorials on the web and then reading the Drupal docs on themeing and studying themes. If you want to develop modules, then you will most likely need intermediate and above knowledge of PHP. But like i said, you can get pretty far with Drupal without ever needing to learn PHP. Huh? That's the same as saying why don't you make your own wheel and then build the car on top of it instead of buying an already made car. If you want to learn PHP and really hone your skills then it makes sense to build your own CMS, but it will take years to develop something the caliber of Drupal or Wordpress.
I think most people feel overwhelmed by Drupal at first. It tends to feel like a steep learning curve when in fact its truly not. The 3 month mention above is pretty accurate for most... Then they hit that "Ah ha!" moment and everything starts to get easier. It really is a great CMS. Add ubercart to it and you have a full ecommerce site without paying for any software.