It's a little weird, usually /externals/scripts folder is used only for javascript-files (and all php-files - inside of /controllers folder).
File .htaccess inside of /externals folder contains a rule
<FilesMatch "\.avi|flv|mov|wmv|wma|mp3|mp4|m4a|mkv|swf|pdf|doc|ppt|ico|jpg|jpeg|png|gif|js|css)$">`
It means that *.php files are not allowed for access inside of this folder.