Unable to Force SSL/https using .htaccess

Question

i'm using open-school php on my host and i'm trying to force ssl on my website but when i add this code

     RewriteEngine On 
     RewriteCond %{SERVER_PORT} 80 
     RewriteRule ^(.*)$ https://www.example.com/$1 [R,L]

but then i'm unable to access my website as the browser says too many loops or redirects

The page isn't redirecting properly

Firefox has detected that the server is redirecting the request for this address in a way that will never complete.

here is the orignal htacess file please help

    Options +FollowSymLinks
IndexIgnore */*
RewriteEngine On


#Admin
Rewriterule ^admin$ index.php?r=Cms/admin/home
#Install
Rewriterule ^install$ install.php?r=Install/default

# if a directory or a file exists, use it directly
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !\.(js|ico|gif|jpg|png|css)$

# otherwise forward it to index.php
RewriteRule . index.php

Answer 1

Rather than using the %{SERVER_PORT} line, try this:

RewriteCond %{HTTPS} !=on

This is a complete .htaccess file that I use to force any website to SSL:

RewriteEngine On
RewriteCond %{HTTPS} !=on
RewriteRule .* https://%{SERVER_NAME}%{REQUEST_URI} [R,L]