[TigerC10]

Consider:

Every single time you load a page from the apache server, you're adding the .htaccess to the program calls. The server has to parse that .htaccess every single time, so the longer it gets the longer it takes to parse. Then it has to go through and compare everything in the request to the values in the .htaccess file. After that, it has to decide what to do based on what it finds. This happens every time you load a page. If apache doesn't find a .htaccess file in the current directory, it goes up a directory and looks in there until it reaches the webroot directory.

It is still more efficient than calling the PHP engine and having it parse the PHP file and then redirectiong, though. That is why the initial http://www.mysite.com/ call is more efficient with .htaccess. However, then the site becomes http://www.mysite.com/forums and it's still parsing and comparing that .htaccess file and its values since there's no .htaccess in the forum directory. Ultimately, that makes the rest of the website run less efficiently.

Using the PHP redirect, you take a slightly heavier hit on the initial request to http://www.mysite.com/, but from there on out when http://www.mysite.com/forums is accessed there's no overhead from the .htaccess file.

One could solve the issue by making a blank .htaccess file in the forums directory, but that's just bad programming practice in my honest opinion.