List WordPress pages in and not in a specific category

stackex_165855.php

<!-- Quick solution for a question on StackExchange,
running through site pages, and compiling a ul of
pages in a category and a ul of pages that aren't. -->

<?php $args = array(
    'post_type' =>  'page',
    'post_status'   =>  'publish',
    'numberposts'   =>  -1
);

//Pull pages into an array
$all_pages = get_posts($args);

//Create empty arrays to populate with filtered pages
$in_category = array();
$ex_category = array();

//loop through the page array
foreach($all_pages as $post) {
    //Set data from the current page as globals,
    //to enable WordPress function tags
    setup_postdata($post);

    //Build the format of the link to be returned
    $link_format = '<li><a href="'.get_the_permalink().'">'.get_the_title().'</a></li>';        

    //Check whether the page is in the category and
    //send this link to the relevant array
    if(in_category(4)) {
        $in_category[] = $link_format;
    } else {
        $ex_category[] = $link_format;
    }   
};

//Restore postdata to before we set it to the current post
wp_reset_postdata(); ?>

<ul class="links_in_category_4">
    <?php foreach($in_category as $cat_link) echo $cat_link; ?>
</ul>

<ul class="links_not_in_category_4">
    <?php foreach($ex_category as $cat_link) echo $cat_link; ?>
</ul>