This .htaccess code allows any uri posted to the html filename in the folder given, to work transparently with the new php system
everything before the extension .html gets posted as $1 to $1.php
old links old bookmarks still work
So basically it's nothing really relevant for the website to function correctly? Because I'm starting from sratch and all the current pages will be erased and replaced with new ones... So I won't really need that .htaccess file, will I?
This has little to do with your NEW site, and much to do with preservation of the old site bookmarks IF a significant number of customers, google, other search engines, backlinks, paid advertising, link to those old file names, the customer will be substantially annoyed if all their existing links fail, with loss of sales, and SER reduction
they will blame you
building from scratch and erasing all current pages is often not an option,
without implementing a system of remapping.
this is what the prior person did with that single .htaccess entry when the client moved from static pages to php
given the above, a 'did you mean new file chosen from a php function of likely candidates please update your bookmarks' is often sufficient,
as is a .htaccess entry that redirects all old files to the new menu system with 301 moved
but is something you should discuss with the client before implementing any alterationwhich also makes it appear you have a tight grasp on the concepts behind seoto cover your behind from later recriminations
and something you should not ignore
I see... Even if the customer is changing their domain name? Is it still applicable?
If yes, then do I need to change anything in the .htaccess file? Because I really need to start from scratch as the old website is unbelievably ugly and has way too many pages and too many directories.
Changed domain name makes it really simple, you can throw away everything, and use a single redirect in the old domain name for a few months to the new menuing system
Your OP said nothing about new domain, sorry all my prior stuff is unneeded
just ask them to keep the old domain name for long enough for google & other se to update links, expired domains are a big business among spammers etc
rewrite code to new domain name