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<?php
/* Shortcode to add parent title above main title if exists */
add_shortcode( 'page_parent', 'output_page_parent' );
function output_page_parent() {
    global $post;
    $post_parentID = $post->post_parent;
    if($post_parentID) {
        $output = '<h4><a href="'.get_permalink( $post_parentID ).'">'.get_the_title( $post_parentID ).' ></a></h4>';
    }
    $output .= '<h1>'.get_the_title( $post ).'</h1>';
    return $output;
}