How to work with $_SERVER['QUERY_STRING']

Question

How to work with $_SERVER[\'QUERY_STRING\'] and pagination?

When my table is sorted by this link:

Answer 1

Instead of reusing QUERY_STRING, you should assemble it anew with http_build_query().

// Merge $_GET with new parameter
$QS = http_build_query(array_merge($_GET, array("page"=>2)));

// You should apply htmlspecialchars() on the path prior outputting:
echo " $i ";

Thus you have all current $_GET parameters included, but can add or replace entries with new values. And it's ensured that each appears only once.