WordPress is_child() for Advanced  Navigation

WordPress lacks one key feature for advanced developers using it as a CMS platform. That feature is the is_child() (or would be) function. If your familiar with WordPress Theme Development you have probably ran into the following Conditional Tags from time to time:

• is_home()
• is_front_page()
• is_single()
• is_sticky()
• is_page()

If you ever want to have a sidebar navigation display the next level of child pages, you would need is_child() to do so.

/**
*   Child page conditional
*   @ Accept's page ID, page slug or page title as parameters
*/
function is_child( $parent = '' ) {
    global $post;

    $parent_obj = get_page( $post->post_parent, ARRAY_A );
    $parent = (string) $parent;
    $parent_array = (array) $parent;

    if ( in_array( (string) $parent_obj['ID'], $parent_array ) ) {
        return true;
    } elseif ( in_array( (string) $parent_obj['post_title'], $parent_array ) ) {
        return true;    
    } elseif ( in_array( (string) $parent_obj['post_name'], $parent_array ) ) {
        return true;
    } else {
        return false;
    }
}

Usage

To use the conditional in your theme(s), add the code above to functions.php. This function now takes the a Post ID, post slug or post title as an argument, so you can use any of the following options:

• is_child(201)
• is_child('Services')
• is_child('our-services')

<?php if( is_child(221) ): ?>

<a href="<?php echo get_permalink(221); ?>">Services</a> &gt; <?php the_title(); ?>

<?php else: ?>

<?php the_title(); ?>

<?php endif; ?>

Deeper functionality

For deeper page tree’s, this is_ancestor() function works well.

<?php
function is_ancestor($post_id) {
    global $wp_query;
    $ancestors = $wp_query->post->ancestors;
    if ( in_array($post_id, $ancestors) ) {
        $return = true;
    } else {
        $return = false;
    }
    return $return;
}
?>

By popular demand, I’ve added a more in depth way to check if a post is a child OR an ancestor of a specific page ID. This hasn’t been tested yet, if it doesn’t work let me know and I can fix it.