get_page_template()

function get_page_template() {
	$id       = get_queried_object_id();
	$template = get_page_template_slug();
	$pagename = get_query_var( 'pagename' );

	if ( ! $pagename && $id ) {
		// If a static page is set as the front page, $pagename will not be set.
		// Retrieve it from the queried object.
		$post = get_queried_object();
		if ( $post ) {
			$pagename = $post->post_name;
		}
	}

	$templates = array();
	if ( $template && 0 === validate_file( $template ) ) {
		$templates[] = $template;
	}
	if ( $pagename ) {
		$pagename_decoded = urldecode( $pagename );
		if ( $pagename_decoded !== $pagename ) {
			$templates[] = "page-{$pagename_decoded}.php";
		}
		$templates[] = "page-{$pagename}.php";
	}
	if ( $id ) {
		$templates[] = "page-{$id}.php";
	}
	$templates[] = 'page.php';

	return get_query_template( 'page', $templates );
}