htaccess restrict access to index.php only - apache

Question

I was writing a .htaccess file for my PHP script.
This should only allow access to the index.php, cronjob.php and execute.php pages.
I wrote the .htaccess file as follows:
# Set default index file
DirectoryIndex index.php
# Disable indexing
Options -Indexes
# Set "403 Forbidden" as the default server behavior
Order Deny,Allow
Deny from all
# Allow requests to core PHP files
<FilesMatch "(index|execute|cronjob)\.php$">
Allow from all
</FilesMatch>
# If mod_rewrite module exists...
<IfModule mod_rewrite.c>
RewriteEngine On
# ...restrict access to PHP private directories
RewriteRule (^|/)logs(/|$) - [F]
RewriteRule (^|/)utils(/|$) - [F]
RewriteRule (^|/)modules(/|$) - [F]
</IfModule>
The main problem with this code is that https://example.com/ returns 403 Forbidden,
while https://example.com/index.php works.

Answer 1

You could put condition to check if a URI is NOT having either index.php OR cronjob.php or execute.php then forbid that page so else other pages will be forbid apart from these 3 php uris.
Please make sure you clear your browser cache before checking your URLs.
RewriteEngine ON
RewriteCond %{REQUEST_URI} !(index|cronjob|execute)\.php [NC]
RewriteRule ^ - [F]

Answer 2

In the end I managed to get it to work, I don't know if it's the best .htaccess possible, but this is what I ended up with:
# Set default index file
DirectoryIndex index.php
# Disable indexing
Options -Indexes
# Set "403 Forbidden" as the default server behavior
Order Deny,Allow
Deny from all
# Allow requests to core PHP files
<FilesMatch "^((index|execute|cronjob)\.php)?$"> # Basically, it accepts the three PHP files and the empty string.
Allow from all
</FilesMatch>