Apache - mod_rewrite. The regex doesn't work correctly. What is the problem? How to write correctly?

Question

Apache HTTP Server

Hello. Didn't work much with apache - mod_rewrite. But now I had to.
The regex doesn't work correctly. For any requests, including /api/blabla/blabla - it returns index.html, but it should be index.php.
Checked here - everything works correctly. But I don't. It seems that the flag [L] does not work. Mb they need to be included somehow?

RewriteEngine on
RewriteRule ^api($|/+.*$) index.php [L]
RewriteRule ^.*$ index.html

(a simplified version of the place that doesn't work)
What I need:
1. If the request starts with /api{whatever else}, then we convert the request to index.php
2. In all other cases, return index.html.
Please help. Thank you very much!

Answer 1

The solution turned out to be this.

RewriteEngine On
RewriteCond %{ENV:REDIRECT_FINISH} !^$
RewriteRule ^ - [L]
RewriteRule ^api($|/+.*$) index.php [E=FINISH:1,L]
RewriteRule ^.*$ index.html [E=FINISH:1,L]

The point was that mod_rewrite could enter an infinite loop.
More about this:
https://habrahabr.ru/post/75885/
https://habrahabr.ru/company/sprinthost/blog/129560/

Answer 2

RewriteRule ^api(.+)$ /index.php [L]
Slash before index