Please help me !

How many days to learn something will vary for every person. It'll depend a lot on how much you apply yourself and also how much of an understanding of it you consider qualifies as learning it.

There is no time to effectively learn something. I've been a programmer since 1992 (started pretty young), and moved to web development (PHP, xHTML, CSS, XML, Javascript, etc) in 2005. I'm still learning new facts every day. Ways to increase security, different functions, etc. Mind you, I also spend hours each day reading through the function reference on php.net.

For the most part, however, I don't really find many PHP books to teach any real-world skills, just code samples with an explanation. I've bought over 20 PHP books to try and find one that taught more advanced concepts, and even that one was rather elementary, or the advanced concepts were useless.

A good place to start is here: http://robert-lerner.com/server.php

This will help you get a server running with MySQL and PHP, which you should use to build up the skill set.

I would give it two years of consistent usage before you can consider yourself able to use PHP to accomplish things you need, but more time to make secure, enterprise-driven applications. Obviously your experience may differ, depending on your technical know-how.