WordPress - Automatically apply a page template to children of a page #WordPress #snippet

apply-parent-page-temmplate.php

/**
 * Automatically apply parent page template
 *
 * Inspired by: http://is.gd/wp_apply_parent_page_template
 */
function fstop_use_parent_page_template() {
	// Checks if current post type is a page, rather than a post
	if ( is_page() ){
		$ancestors = get_post_ancestors( get_the_id() );

		if ( $ancestors ) {
			$parent_page_template = get_post_meta( end( $ancestors ), '_wp_page_template', true );
			$template = TEMPLATEPATH . "/{$parent_page_template}";
			$current_page_template = get_post_meta( get_the_id(),'_wp_page_template', true );

			if ( file_exists( $template ) ) {
				load_template( $template );
				update_post_meta( get_the_id(), '_wp_page_template', $parent_page_template, $current_page_template );
				exit;
			}
		} else {
			return true;
		}
	}
}
add_action( 'template_redirect', 'fstop_use_parent_page_template' );