Passing a URL variable to category.php - php

Question

I need to pass a URL variable to my category.php file.
Currently my category page is at http://example.com/category-slug/
I am using the SEO plugin to rewrite http://example.com/category/category-slug and remove the /category/ part.
Also, the settings formy permalinks are set to this option in the settings menu: http://example.com/sample-post/
Now I need to be able to pass a variable in the URL like:
http://example.com/category-slug/?type=VALUE
or
http://example.com/category-slug/VALUE
where "type" is the name of the variable and VALUE is its value
I have tried using this piece of code in my functions.php file:
<?php
add_filter('query_vars', 'parameter_queryvars' );
function parameter_queryvars( $qvars )
{
$qvars[] = 'type';
return $qvars;
}
global $wp_query;
if (isset($wp_query->query_vars['type']))
{
print $wp_query->query_vars['type'];
}
?>
However, when I try to open http://example.com/category-slug/?type=something or http://example.com/category-slug/something I get "nothing found" and "Page not found" pages.
While I see this has been discussed over and over, none of the solutions seem to work for my case.
How do I properly pass a variable to a category page?

Answer 1

First of all, you code will never reach the if statement, as you return from the function before.
I also don't know which SEO tool you are using, but there is one function that goes with the "query_vars" filter: add_rewrite_rule()
I would recommend to write a little plugin which does the rewriting of the category permalink. Something like this (untested, but similar to a plugin I use):
// Flush added rewrite rules on activation
function category_permalink_rewrite_activate() {
category_permalink_rewrite_set_rewrite_rules();
flush_rewrite_rules();
}
register_activation_hook( __FILE__, 'category_permalink_rewrite_activate' );
// Remove rewrite rule for event archives
function category_permalink_rewrite_deactivate() {
flush_rewrite_rules();
}
register_deactivation_hook( __FILE__, 'category_permalink_rewrite_deactivate' );
// Add rewrite rule for category permalink on init
add_rewrite_rule( '^category-(.*)/(.*)', 'index.php?category_name=$matches[1]&type=$matches[2]', 'top' );
kaufunction category_permalink_rewrite_set_rewrite_rules() {
}
add_filter( 'init', 'category_permalink_rewrite_set_rewrite_rules' );
// Register the custom query var so WP recognizes it
function category_permalink_rewrite_add_query_vars( $vars ) {
$vars[] = 'type';
return $vars;
}
add_filter( 'query_vars', 'category_permalink_rewrite_add_query_vars' );