How to create custom LOGIN and REGISTRATION forms?

Question

I have developed a theme for Wordpress and I need to customize login and registrations form. At the moment, as usual, the login and the registration URL are:

http://www.example.com/wp-login.php
http://www.example.com/wp-login.php?action=register

I would like to create INLINE form, with INLINE I mean that this form must to be inside my pages and not in a single(dedicated) web page.

For login I need:

- Email 
- Password

For Registration:

- Name
- Email
- Password
(and a pseudo check for "spammers" like captcha or arithmetical operations)

as I told I need these forms in my pages, not in a dedicated page.

Two questions:

1- Can I do it WITHOUT using a plugin?

2- If I can, how can I show any errors (example: wrong email, wrong password) inline with the form? (without redirect to wp-login.php)

Thank you!

Answer 1

1. Can you do it without a plugin?

Certainly. Anything a plugin can do, you can obviously also implement yourself.

1.1 Should you do it without a plugin?

No. This is clearly plugin-territory. Even if you want to write the plugin yourself, this would be a better fit for a custom plugin than to incorporate it in your theme. That's a matter of preference and opinion though - of course it can be done within your theme also.

For the sake of completeness, let me mention Jeff Farthing's theme-my-login. It's a well written, powerful plugin that has been developed for years. It is for sure the (much) less work-intensive solution and you should at least consider using it before you hack away on writing something similar (and most likely less powerful).

2. How can it be done?

Have a look at the Administrative Actions and hook into those.

Again consider downloading the above mentioned plugin and dissect how it works.