Detect if a page have been called via .htaccess RewriteRule in PHP

[toNixx]

I am using .htaccess \[code\]RewriteRule\[/code\] on a website I'm working on.Here is a sample of my .htaccess\[code\]RewriteEngine onRewriteRule ^about.htm$ /index.php?load=about&output=html [NC]\[/code\]I would like to know if there is a way in my \[code\]index.php\[/code\] file to detectif the page have been called via a Rewrite or the user reached itdirectly. I'm trying to avoid having to write some security check thatI am not even sure where to start.If there is no way to make that "check" where should I start to securethe file ?My guess would be to make sure only \[code\]load\[/code\] and \[code\]output\[/code\] arepassed to the \[code\]$_GET\[/code\], make a \[code\]strip_tags()\[/code\], \[code\]trim()\[/code\], \[code\]stripslashes()\[/code\] and remove quotes.Thank you!