How to display working php page name in WordPress ?

To display display working php page name in WordPress
add below code in header.php inside theme folder

 echo  get_page_template()."gggggggggg";
     exit;

See out put

 OUTPUT "/wp-content/themes/twentyseventeen/pages.phgggggggg"

default build in functon is located inside ‘wp-includes/template.php’ folder

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 );
}