htaccess - protect php file execution in specific directory

How can I protect php execution in specific upload directory?

Mostly, people put .htaccess in upload folder to protect php execution. But someone says it can be replaced by attackers.

So how can I control it from the root .htaccess ?

I tried to put the below codes in root .htaccess but it shows "500 internal sever error" and my website goes down.

<Directory ^public_html/product/uploads>
<Files ^(*.php|*.phps)>
    order deny,allow
    deny from all
</Files>

Thanks in advance