Question

I need to list posts by category, but only for posts which have a given tag (or tags). So far I have the following code, which works fine for listing ALL my posts grouped by category, but I’m not sure how to modify it to only select posts with a given tag. What should I change?

 <?php           
        // get all the categories from the database
        $cats = get_categories(); 

            // loop through the categries
            foreach ($cats as $cat) {
                // setup the cateogory ID
                $cat_id= $cat->term_id;
                // Make a header for the cateogry
                echo "<h2>".$cat->name."</h2>";
                // create a custom wordpress query
                query_posts("cat=$cat_id&post_per_page=100");
                // start the wordpress loop!
                if (have_posts()) : while (have_posts()) : the_post(); ?>

                    <?php // create our link now that the post is setup ?>
                    <a href="<?php the_permalink();?>"><?php the_title(); ?></a>
                    <?php echo '<hr/>'; ?>

                <?php endwhile; endif; // done our wordpress loop. Will start again for each category ?>
            <?php } // done the foreach statement ?>

Answer 1

All you need to do is edit your query to include the tag, i.e.
query_posts("cat=$cat_id&tag=tag1+tag1&showposts=100");

Note you need all of tag1+tag1