Question

I’d like to create a link that changes a PHP $_GET variable. For example:

URL: http://site.com/index&variable=hello&anothervariable=dontchangeme

<a href="variable=world">Click me</a>

(after click)

URL: http://site.com/index&variable=world&anothervariable=dontchangeme

I know you can do this to just change the page (href="1.html"), but I’d like to do the same thing while maintaining the GET variables that were already there.

Answer 1

$query = array('variable' => 'world') + $_GET;

printf('<a href="index?%s">Click me</a>', http_build_query($query));

See http://php.net/http_build_query. That’s the easy to understand minimal version. Correctly you need to also HTML-escape the generated query string (because you’re putting it into HTML):

printf('<a href="index?%s">Click me</a>', htmlspecialchars(http_build_query($query)));