How can I add GET variables to the end of the current page url using a form with php?

I have some database information that is being shown on a page.

I am using a pagination class that uses the $_GET['page'] variable in the url. When you click on a different pagination anchor tag, it changes $_GET['page'] to a new number in the url and shows the corresponding results.

I have sort and search features which uses the $_GET['searchby'] and $_GET['search_input'] variables. The user enters their search criteria on a form that is using GET. The variables are then put into the url allowing for the correct results to be shown.

The problem I am having is that whenever I click on a pagination link, it开发者_运维技巧 adds the $_GET['page'] variable to end of the url and erases $_GET['searchby'] or $_GET['search_input']. When I submit the search form, it adds $_GET['searchby'] and $_GET['search_input'] but erases $_GET['page'].

How can I add GET variables to the end of the current page url using the anchor tag and search/sort form without having it erase any existing GET variables, but overriding them if they're the same GET variable name?

Try this:

if (strpos($_SERVER['REQUEST_URI'], '?') !== false)
{
  $url = $_SERVER['REQUEST_URI'] . '&var=value';
}
else
{
  $url = $_SERVER['REQUEST_URI'] . '?var=value';
}

<a href="<php echo $url;>">Go</a>

Note that $_SERVER['REQUEST_URI'] gives you current url including query string value.

$query_string = http_build_query(array_merge($_GET, array('page' => $page)));