Rewriting url with the following regular expression - mod-rewrite

Question

I'm trying to do a mod rewrite to get this url: localhost/test/index.php?hello
I created a file for this page called hello.php and it is in the folder /test
To clarify, I have another page that has a link to my hello.php, but what is the correct url so I can display localhost/test/index.php?hello in the url when I click the link to access my hello.php page.
The following doesn't seem like it is right:
RewriteRule ^.*$ index.php?$1 [L]

Answer 1

Try this if you want to just do php files.
RewriteEngine on
RewriteRule (.*)\.php$ /index.php?$1 [L]
To clarify what my answer does. It gives you more friendly URLs which it sounded like what your were asking for.
So you can use localhost/hello.php and it will be internally redirect to /localhost/index.php?hello. Internally means they will never see localhost/index.php?hello and will always see localhost/hello.php in their browser.
You can do any URL and it will rewrite to a php file. e.g. localhost/index.php?newpage and you can use /localhost/newpage.php
Hope that is clearer.
EDIT
You want the reverse but I don't know how your PHP is constructed but query strings are typically field/value pairs. For example name=john, page=contact, action=hello etc. You have index.php?hello but hello has no content or value.
That's probably why you're having such a hard time even re-writing your URL. Using $_GETwould require a value.
So what I would do, is if your URL was like this using field/value pairs
index.php?action=hello
Then in the index.php file you could do something like
$action = $_GET["action"];
if($action == "hello"){
//show contents of hello, include a page or whatever
}
Once you have good URLs it would be easy to rewrite it.
So if the URL that you want shown is like
index.php?action=hello and you want to redirect it to hello.php
Your .htaccess would look like this
RewriteRule ^action=([^/]+) /$1.php [R,L]
That would redirect it to the php file. If you don't want to show the redirection and keep it an internal redirect you can remove the R flag and just keep [L].
I personally don't want the user to see really long query strings URL example. mysite.com?page=music&artist=someartist&title=sometitle
So all my URL's are rewritten to be shorter and friendlier like my original answer.

Answer 2

you don't need .htaccess for 2. as far as you're using GET parametr - use it in index.php:
if (isset($_GET['hello'])) include('hello.php');
this will show the contents of hello.php inside index.php