Is there any forms out there that support things such as user administration, pagination, form validations, and similar things to that? Also paypal frameworks, and etc? What would you guys recommended?
Most frameworks support pagination, form validation and similar features. As for Paypal integration, you'd probably need a plugin for that sort of thing. I'd suggest looking at the following frameworks to see if they do what you want: CakePHP CodeIgniter Symfony Zend Framework
i didn't see that zend had one things such as user admin and etc. I've always built mine own frameworks honestly.
They don't specifically have admin authentication but they will have session and security modules. You'll need to use these to authenticate the users.
wel i never used any framework, i just code simple in dreamweaver, please explain me what is php framework and why we use it?
A PHP frame work is just a set of useful PHP classes to make the development of PHP applications easier and faster. It is not going to make an entire application for you and it shouldn't. So for example you want to make PDF's well part of Zend's framework includes a PDF generation and modification system. Does it make it super easy to make pdf's? of course not but it makes it easier than doing it without any help at all.
Frameworks just speed development time up so for example you have a client thats wanting a website and your charing him 10k why not have it done in two weeks by using frameworks and some of your own code vs writing all your won code. Either way if your good with coding php you can write your own frameworks, and reuse them, but reguardless when using a new framework you have to have some understanding of it or at least get famaliar with it, but all that will come with time. There is still stuff i struggle with and I've been working with php on and off my whole life time, but really started using it the last year half.
CakePHP is a great framework to use. Really shortens the development time. But in the end, you do still need to program. Its just a framework for rapid development.
Decent list: http://www.phpit.net/article/ten-different-php-frameworks/ Of course it's not near the total number of ones that are being used by various people.