Group Posts by First Letter of Title

Question

once up a time i did a client project where i had to have archives by first letter. thinking back i’m wondering if shouldn’t have just created a hidden taxonomy and then saved the first letter as a term in that taxonomy.

anyway, here’s what i actually did:

/*
 * Function Create Array of Letters that have post titles (for archive)
 */

/* When the post is saved, saves our custom data */
function kia_save_first_letter( $post_id ) {
    // verify if this is an auto save routine. 
    // If it is our form has not been submitted, so we dont want to do anything
    if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) 
        return;

    //check location (only run for posts)
    $limitPostTypes = array('post');
    if (!in_array($_POST['post_type'], $limitPostTypes)) return;

    // Check permissions
    if ( !current_user_can( 'edit_post', $post_id ) )
        return;


    // OK, we're authenticated: we need to find and save the data
    $alphabet = get_option( 'kia_alphabet_archive' );

    $alphabet = is_array($alphabet) ? $alphabet : array($alphabet);

    // pop off first letter of post title
    $letter = substr($_POST['post_title'], 0, 1);

    // if it doesn't exist, add it to array
    if(!in_array($letter, $alphabet))
        $alphabet[] = $letter;
        sort($alphabet);

    $alphabet = is_array($alphabet) ? array_unique($alphabet) : array($alphabet);

    update_option( 'kia_alphabet_archive', $alphabet );
}
add_action( 'save_post', 'kia_save_first_letter' );

if you have posts already before adding this you’ll need to run the following once to grab the first letters for the existing posts:

//create array from existing posts
function kia_run_once(){
    $alphabet = array();
    $posts = get_posts(array(   
            'numberposts'     => -1
            ) );

    foreach($posts as $p) :  
        $alphabet[] = strtoupper(substr($p->post_title, 0, 1)); //first letter of post title, capitalized 
    endforeach;

    sort($alphabet);

    update_option( 'kia_alphabet_archive', array_unique($alphabet) );

}
add_action('init','kia_run_once');

now we need some stuff to decipher when were are on a custom archive page and what to do differently

/*
 * Custom Archives by KIA
 */

function archive_queryvars( $qvars ) {
    $qvars[] = 'showarchive';
    return $qvars;
}
add_filter('query_vars', 'archive_queryvars' );


function is_custom_archive() {
    global $wp_query;
    return isset( $wp_query->query_vars['showarchive'] );
}

function archive_search_where( $where ){
    global $wpdb;

    if( is_custom_archive() ) {
        $char = get_query_var('showarchive');
        if ( ! empty($char) ) {
            $where .= "AND {$wpdb->posts}.post_title LIKE '{$char}%'";
        }
    } 
  return $where;
}
add_filter('posts_where', 'archive_search_where' );

little helper function to make links

/* 
 * add archive query arg to link
 */
function get_custom_archive_link($char="") {
    $params = array(
            'showarchive' => $char,
            );
    return add_query_arg( $params, home_url("https://wordpress.stackexchange.com/") );
}

now create our custom archive menu

$alphabet = get_option ('kia_alphabet_archive');

if(count($alphabet)>0){ ?>
    <div id="archive-menu" class="menu">
    <?php for ($i=65; $i < 91; $i++) : 
            $current = (chr($i) == get_query_var('showarchive')) ? "current-menu-item" : "menu-item";

            if (is_array($alphabet) && in_array(chr($i), $alphabet)){ ?>
                <li class="az-char <?php echo $current;?>">
                    <?php printf('<a href="https://wordpress.stackexchange.com/questions/41660/%s">%s</a>', get_custom_archive_link(chr($i)), chr($i) ) ?>
                </li>
            <?php } else { ?>
                <li class="az-char <?php echo $current;?>">
                    <?php echo chr($i); ?>
                </li>
            <?php } ?>  

            <?php endfor; ?>
    </div>
<?php }

clicking on the links should now bring you to a page that only shows posts that state with that letter.

looking back i think the taxonomy idea would be a lot less code and have cleaner rewrite support built-in from the beginning (ie… no query vars, even though those could be re-written… i don’t know how). the taxonomy approach would also add tax data to the DB, whereas this only adds the one option. so trade-off?

*EDIT**

ok, i took a stab at the taxonomy route and it is slightly more elegant like i expected

first register the taxonomy. i have this only running on posts, but you could easily mod it to suite whatever post type you’d like.

// Add new taxonomy, NOT hierarchical (like tags)
function kia_create_glossary_taxonomy(){
    if(!taxonomy_exists('glossary')){
        register_taxonomy('glossary',array('post'),array(
        'show_ui' => false
      ));
     }
}
add_action('init','kia_create_glossary_taxonomy');

similar save function to store our tax data when a post is saved

/* When the post is saved, saves our custom data */
function kia_save_first_letter( $post_id ) {
    // verify if this is an auto save routine. 
    // If it is our form has not been submitted, so we dont want to do anything
    if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) 
        return;

    //check location (only run for posts)
    $limitPostTypes = array('post');
    if (!in_array($_POST['post_type'], $limitPostTypes)) return;

    // Check permissions
    if ( !current_user_can( 'edit_post', $post_id ) )
        return;


    // OK, we're authenticated: we need to find and save the data
    $taxonomy = 'glossary';

    //set term as first letter of post title, lower case
    wp_set_post_terms( $post_id, strtolower(substr($_POST['post_title'], 0, 1)), $taxonomy );

    //delete the transient that is storing the alphabet letters
    delete_transient( 'kia_archive_alphabet');
}
add_action( 'save_post', 'kia_save_first_letter' );

again need to run something once to grab old posts, remove when done

//create array from existing posts
function kia_run_once(){
    $taxonomy = 'glossary';

    $alphabet = array();
    $posts = get_posts(array('numberposts' => -1) );

    foreach($posts as $p) :  
        //set term as first letter of post title, lower case
        wp_set_post_terms( $p->ID, strtolower(substr($p->post_title, 0, 1)), $taxonomy );
    endforeach;     
}
add_action('init','kia_run_once');

add the menu this was the only part that wasn’t totally elegant, as it wasn’t straightforward to test whether a term had posts w/o the extra foreach loop. but i have mitigated that by storing it in a transient that only resets on post save.

$taxonomy = 'glossary';  

// save the terms that have posts in an array as a transient
if ( false === ( $alphabet = get_transient( 'kia_archive_alphabet' ) ) ) {
    // It wasn't there, so regenerate the data and save the transient
    $terms = get_terms($taxonomy);

    $alphabet = array();
    if($terms){
        foreach ($terms as $term){
            $alphabet[] = $term->slug;
        }
    }
     set_transient( 'kia_archive_alphabet', $alphabet );
}

?>

<div id="archive-menu" class="menu">
    <?php foreach(range('a', 'z') as $i) : 
            $current = ($i == get_query_var($taxonomy)) ? "current-menu-item" : "menu-item";

            if (in_array( $i, $alphabet )){ ?>
                <li class="az-char <?php echo $current;?>">
                    <?php printf('<a href="https://wordpress.stackexchange.com/questions/41660/%s">%s</a>', get_term_link( $i, $taxonomy ), strtoupper($i) ) ?>
                </li>
            <?php } else { ?>
                <li class="az-char <?php echo $current;?>">
                    <?php echo strtoupper($i); ?>
                </li>
            <?php } ?>  

        <?php endforeach; ?>
</div>

so there are 2 solutions. the latter will get your URLs to say site.com/glossary/l without any htaccess rules to re-write query vars on your part. hope that helps.

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