[WP] Postlist navigation by category

<?php

// set category list
$categories = array('collections', 'special_projects', 'press');

// start building an array of post listings by category
$cat_nav = array();

foreach ( $categories as $category ) {

    // get category data
    $category = get_term_by( 'slug', $category, 'category' );

    // start building link
    $cat_nav[$category->slug] = "<li><a href='#' id='link_for_list_of_{$category->slug}'>{$category->name}</a>";

        // build list
        $cat_nav[$category->slug] .= "<ul id='list_of_{$category->slug}'>";

        // get posts from category
        $myposts = get_posts('category_name=' . $category->slug);

        foreach ( $myposts as $mypost ) {

            // add each link to the array
            $cat_nav[$category->slug] .= "<li><a href='" . get_permalink($mypost->ID) . "'>" . get_the_title($mypost->ID) . "</a></li>\n\n";

        }

        $cat_nav[$category->slug] .= "</ul>";

    $cat_nav[$category->slug] .= "</li>";

}


// now let's build nav menu
$navmenu = "<ul id='nav'>";

    $navmenu .= $cat_nav['collections'];

    $navmenu .= $cat_nav['special_projects'];

    $navmenu .= wp_list_pages('include=26,18,20&title_li=&echo=0');

    $navmenu .= $cat_nav['press'];

    $navmenu .= wp_list_pages('include=7,24&title_li=&echo=0');

$navmenu .= "</ul> <!--end of Nav-->";

// and print it out
echo $navmenu;