RedirectMatch并隐藏URL

Let's say there is a webpage called me.com where I want the file from /project/index.php to be the main root file.

/project/index.php looks like this:

<?php
header('Location: /project/site-one.html');
exit;
?>

the .htaccess looks like this:

<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteBase /
    RedirectMatch ^/$ /project/index.php [L]

    # more rules follow

now if I visit me.com I get me.com/project/site-one.html

What I want is, always if there is /project/site-one.html or /project/index.php to just show me.com in the adressbar as URL.

How is this possible? I've tried with RewriteRule and just passing the [L] flag but nothing does what I want.

You can use .htaccess like this in root .htaccess (a level above project):

RewriteEngine On
RewriteRule ^/?$ /project/site-one.html [L]

You should remove header(...) function call from your index.php