From few months I am digging into wordpress for multiple category search options, and finally came up with this.

I just found that wordpress allows multiple tags, which means that if in your URL you type this


then it will return all your posts with having tags, tag1 AND tag2

but if you type


then it will return all the posts having tag1 OR tag2

Same thing now works for categories also

http://yourblog.com/category/cat1+cat2 and http://yourblog.com/category/cat1,cat2

But this only works for category and tags, I am trying it for search option.

Till now I coded where this URL is working(which means it will search HTML only in the category id 114),


In this URL, the comma separator works very well, but not the +

I mean to say


works very well but


doesn't works.

Can anyone help me in this? I really want this to work

Still awaiting

  • Can anyone help me in this?????????? Commented Aug 30, 2011 at 4:41

3 Answers 3


The problem is that in a url the '+' sign is equivalent to a space so that's how PHP sees it.

If you use an action on parse_request you can make this work like so:

add_action( 'parse_request', 'category_search_logic', 11 );
function category_search_logic( $query ) {

    if ( ! isset( $query->query_vars[ 'cat' ] ) )
        return $query;

    // split cat query on a space to get IDs separated by '+' in URL
    $cats = explode( ' ', $query->query_vars[ 'cat' ] );

    if ( count( $cats ) > 1 ) {
        unset( $query->query_vars[ 'cat' ] );
        $query->query_vars[ 'category__and' ] = $cats;

    return $query;

The above will get category ids passed in with '+' in between them by splitting them on a space which is what PHP sees in the $_GET parameter.

If we have more than one item in the array it must be an 'and' style search so we can pass the array from splitting on the space into the 'category__and' query var which returns posts in all the specified categories.

  • I think you need a hats off from my side, this actually worked, at last now I can have multiple category search on my sites Really really thankful to you :) Commented Oct 31, 2011 at 17:39
  • @ntechi My pleasure :) Commented Nov 1, 2011 at 11:33

Try this: http://yourblog.com/?s=html&cat[]=114&cat[]=115

BTW, why don't you use a hook link pre_get_posts to filter your search? It would be much easier than tweaking the search URL.

  • Itried the cat[]=114&cat=115 but not working, and can you explain me what to do with pre_get_posts I am not getting you Commented Sep 1, 2011 at 4:09

The solution suggested by @sanchothefat is OK, but leads to problems when pagination is used. For example, you have url like domain.com/?s=&cat=1+2. When you click on page 2, the URL become domain.com/?s=&cat=1+2 but redirect_canonical() defined in wp-includes/canonical.php tries to modify url to domain.com/?s&cat=12 which is not the same... I found easier to me to rewrite category_search_logic() rather investigate redirect_canonical() logic and apply additional filters to it.

This is my way to buypass the canonical logic:

function category_search_logic( $query ) {
    if ( ! isset( $_GET['categories'] ) )
        return $query;

    // split cat query on a space to get IDs separated by ',' in URL
    $cats = explode(',', $_GET['categories'] );

    if ( count( $cats ) > 1 ) {
        $query->query_vars[ 'category__and' ] = $cats;

    return $query;

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