Upgrading php via htaccess

Hello

I am having issues with installing a themes or plugins. I have been told that its because I need to have a newer version of php installed. My hosting company hasnt upgraded yet and they are still using 5.4.24

Researching shows that I can add code to htcaccess and that it will fix the problems. So this is what I have,

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# Use PHP 7.1
AddType application/x-httpd-php71 .php
# END WordPress

The problem now is that when I try to go to the site my browser creates a download dialogue box to download files instead of displaying them. What am I doing wrong?

Thanks