What are potential pitfalls when using the QSA flag in mod_rewrite for passing additional query strings in PHP?

When using the QSA flag in mod_rewrite to pass additional query strings in PHP, a potential pitfall is that it may result in duplicate query parameters if not handled correctly. To solve this issue, you can use the PHP `$_SERVER['QUERY_STRING']` variable to merge the existing query string with the additional parameters being passed. 

RewriteEngine On
RewriteCond %{QUERY_STRING} !^$
RewriteRule ^(.*)$ /$1?%{QUERY_STRING}&additional_param=value [QSA]

Keywords

mod_rewrite QSA flag query strings PHP pitfalls

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